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{{Era|H1|H2|H3|TF|FS|HGN|FA}}
{{Status|Canon}}
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{{Center|"Halo" redirects here. For other uses, see [[Halo (disambiguation)]].}}
:''“Installations” redirects here. For other uses, see [[Installation (disambiguation)|Installation]].''<br /><br />
[[File:TerminalArkArray.jpg|thumb|300px|The Array at [[Installation 00]], just before their departure to firing sites across the galaxy.]]
{{Quote|Weapons of last resort. Built by the Forerunners to eliminate potential Flood hosts, thereby rendering the parasite harmless.|[[343 Guilty Spark (Monitor)|343 Guilty Spark]]}}
{{Quote|Halo doesn't kill Flood, it kills their ''food!'' Humans, Covenant, whatever—we're all equally edible! The only way to stop the Flood is to starve them to death. And that's exactly what Halo is designed to do: wipe the galaxy clean of all sentient life!|[[Cortana]] during the [[Battle of Installation 04]]}}.{{Ref/Level|Id=TB|HCE|Two Betrayals}}
[[Image:Installation 05.jpg|right|thumb|290px|"Whoever controls Halo controls the fate of the universe." - Captain Keyes.]]The '''Halos'''<ref>[[Halo: Combat Evolved]], level [[Truth and Reconciliation (Level)|Truth and Reconciliation]]</ref> (as they are commonly referred to based on intercepted [[Covenant]] transmissions<ref>[[Halo: The Flood]] page 38</ref>), alternatively known as the '''Sacred Rings'''<ref>[[Halo 2]], level [[Gravemind (Level)|Gravemind]]</ref> by the Covenant, '''Fortress Worlds'''<ref>[[Halo: The Flood]] page 193</ref> by their creators, and '''Installations''' by the [[AI]] [[Monitors]] that run them, are seven massive ring-shaped installations constructed by the [[Forerunner]] throughout the galaxy over one hundred thousand years ago as a last resort when combating the parasite known as the [[Flood]]. When nothing else could be done, they activated the rings which killed all sentient life within three radii of the galactic center. In addition to their role as [[weapons]] of last resort, the Halo installations are also research facilities. These facilities are chiefly used for studying the Flood.
 
The '''Halo Array''', sometimes known simply as '''Halo'''<ref>''[[Halo: Warfleet]]'', p. 92</ref> or '''the Array''',<ref>'''[[Halo 3]]''', ''[[Terminal (Halo 3)|Terminal Four]]''</ref><ref>'''[[Halo: Combat Evolved Anniversary]]''', ''[[Terminal (Halo: Combat Evolved Anniversary)|Terminal Two]]''</ref> is a network of colossal ring-shaped superweapons individually known as '''Halos''' or '''Halo rings''', constructed by the [[Forerunner]]s.{{Ref/Level|Id=TC|HCE|The Truth and Reconciliation}} The Halos were also referred to by the [[Covenant]] as the '''Sacred Rings''',<ref>'''Halo: The Flood''', page 38</ref>{{Ref/Level|Id=gravemind|H2|Gravemind_(level)}} and labeled as '''Installations''' or infrequently referred to as Fortress Worlds<ref>'''Halo: The Flood''', ''page 193''</ref> by the Forerunners and their [[monitor]]s.
 
The first array of twelve Halos was constructed by order of [[Master Builder]] [[Faber]] circa [[98,445 BCE]] with the intent of being an ultimate weapon, one that would secure the preeminence of the [[Builder]] [[rate]] in Forerunner society.<ref name="c274">'''Halo: Cryptum''', ''page 274''</ref> Later, the weapons would be refined further and a new array of six smaller and significantly more lethal installations was constructed; the newer Halos are known as the "neoteric" rings.{{Ref/Site|Id=neoteric|URL=https://www.reddit.com/r/halo/comments/70wbxc/return_to_the_denomination_installation_04_b_c/dn76nzc/|Site=Reddit|Page=Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS|D=18|M=9|Y=2017}} Eventually, eleven were destroyed and/or lost while the remaining [[seven]] were used by the Forerunners as a last resort when combating the parasitic [[Flood]].{{Ref/YouTube|Id=Lorestream|fYaxRoAf96s|HALO|Halo Lore Stream: The Halo Array|Y=2018|M=04|D=06|343 discuss the Halo Array}} All [[sentience|sentient]] beings in the galaxy were killed, robbing the Flood of hosts and starving it to death.
 
In addition to serving as weapons of last resort, Halo installations are also research facilities dedicated to containing and studying many different kinds of life forms. The life forms that were hand-selected by the [[Librarian]] included marine life, fauna, and land vertebrates. With the Master Builder's permission, the Librarian would research each animal to detect if their bodies reacted to Flood infection. The research on the animals would be more deeply analyzed if they did become infected. The Librarian's studies also helped determine if the rings could be used to repopulate the galaxy as part of the [[Conservation Measure]].{{Ref/Reuse|Lorestream}}<ref name="c313">'''Halo: Cryptum''', ''pages 313, 334''</ref>


==Background==
==Background==
[[Image:SevenHalos.jpg|thumb|right|200px|Readout of the [[seven]] Halos]]
[[File:Halo Surface.jpg|thumb|200px|A section of a Halo's surface.]]
[[Image:Delta Halo.jpg|thumb|right|200px|One of the [[seven]] Halos]]
{{Quote|After exhausting every other strategic option, my creators activated the rings. They, and all additional sentient life in three radii of the galactic center, died, as planned.|[[343 Guilty Spark]] during the [[Battle of Installation 05]]}}.{{Ref/Reuse|great journey}}
As it is known in modern times, the Halo Array is a network of seven ring-shaped megastructures created by the Forerunners, designed to exterminate all sentient life within the Milky Way galaxy.{{Ref/Level|Id=great journey|H2|The Great Journey}} Built following the [[Human-Forerunner War]], these ringworlds were later used as a last resort against the Flood, a parasitic extra-galactic species that threatened to consume every sentient life-form in the galaxy. By activating the rings, the Forerunners wiped out every sentient being in the galaxy, effectively starving the Flood to virtual extinction, though specimens were kept in a number of Forerunner [[Flood containment facility|containment facilities]], including the Halo installations themselves.{{Ref/Level|Id=library|HCE|The Library}}
 
A total of eighteen Halo rings existed during the reign of the Forerunners; an older array of twelve 30,000-kilometer-wide rings produced by the [[greater Ark]] and six 10,000-kilometer rings, constructed at the newer [[Installation 00|lesser Ark]]. Of these, only seven survived to be included in the final Array. The Halos were originally deployed in orbit over large gas giants.<ref name="gas giants">'''Halo: Silentium''', ''page 237''</ref> However, as of [[2557]], [[Installation 03]] orbited a rocky planet.{{Ref/Level|Id=h4composer|H4|Composer_(level)}} Installation 04 maintained an atmospheric [[Threshold gas mine|mining facility]] in its anchor planet [[Threshold]]'s atmosphere until [[Battle of the Threshold gas mine|it was destroyed]] by the [[Covenant]].{{Ref/Level|Id=The Oracle|H2|The Oracle}}
 
Though separated by thousands of light-years, the installations are networked together and capable of remote activation at [[Installation 00|the Ark]], their [[intergalactic space|extragalactic]] construction foundry. Each Halo installation has a maximum effective range of 25,000 light-years in every direction.<ref>'''Halo: Combat Evolved Anniversary''', ''[[Terminal (Halo: Combat Evolved Anniversary)#Terminal 8|Terminal 8]]'' (''"25,000 light years. That is the effective range of this installation."'')</ref><ref name="radius">'''[[Halo: Combat Evolved]]''', level ''[[Two Betrayals]]'', 343 Guilty Spark: ''"Technically, this installation's pulse has a maximum effective radius of 25,000 light years."''</ref> The method utilized by the array to conduct this "mass sterilization protocol"<ref>'''[[Halo: Combat Evolved]]''', level ''[[The Library]]'', 343 Guilty Spark: ''"Why the Flood is, naturally, simply too dangerous to release, and mass sterilization protocols may again need to be enacted."''</ref> involves the superluminal conveyance of a burst of cross-phased super-massive neutrinos, tuned to emit a harmonic frequency that destroys the nervous system of any life form within range. Simpler organisms lacking a neural system are unaffected, along with inanimate structures. [[Precursor]] technology, however, is extremely susceptible to damage from the Halo effect due to its quasi-living [[neural physics]] composition.{{Ref/Reuse|c274}}<ref>'''Halo: Cryptum''', ''page 132''</ref>
 
[[File:H2A - Halo Array hologram.jpg|left|thumb|250px|Readout of the seven Halos.]]
The Halo Array in its entirety has been fired only once in known history, approximately 100,000 years ago, by the [[IsoDidact]] in order to stop the Flood from overwhelming the galaxy. All beings in the Array's effective range, including Forerunners themselves, were wiped out by the Array's pulse,{{Ref/Reuse|great journey}} with the exception of those who took refuge on the [[shield world]]s. A number of Forerunners survived at the lesser Ark but chose to exile themselves from the galaxy.<ref name="rebirth">'''Halo: Rebirth'''</ref> The array has come close to activation four times since; Installation 04 was almost activated by the [[John-117|Master Chief]], Installation 05 was activated by Commander [[Miranda Keyes]] at the behest of the [[Jiralhanae]] [[Chieftain of the Jiralhanae|Chieftain]] [[Tartarus]], [[Avery Junior Johnson|Sergeant Johnson]] was forced by the [[Prophet of Truth]] to activate the Array from the Ark, and [[Bobby Kodiak]] was forced by [[000 Tragic Solitude]], the Monitor of the Ark, to activate the Halo Array from the Ark as a revenge. None of these attempts were successful; the first was stopped by Cortana, while the other three attempts were halted by UNSC and [[Swords of Sanghelios|Sangheili]] intervention. A [[Installation 08|replacement]] Halo for the destroyed Installation 04 was activated outside of the galaxy, meant to eliminate the Flood massed at [[Installation 00]]. Upon firing, its incomplete state caused the ring to shake itself to pieces, with the resulting explosion damaging the Ark. However, some Flood forms survived the activation.{{Ref/Site|Id=IntroducingATN|URL=https://www.halowaypoint.com/en-us/news/introducing-halo-wars-2-awakening-the-nightmare|Site=Halo Waypoint|Page=Introducing Halo Wars 2: Awakening the Nightmare|Quote=While most of the Flood threat was destroyed in the crash of High Charity and in the explosive end of Halo 3, even the smallest remaining spore of Flood can take over the galaxy, given enough time.|D=29|M=09|Y=2021|LocalArchive=https://archives.halopedia.org/waypoint/www.halowaypoint.com/en-us/news/introducing-halo-wars-2-awakening-the-nightmare.html}}


The Halo Array is a network of seven<ref>343 Guilty Spark: "Collectively, the seven-"</ref> [[Wikipedia:Orbitals (The Culture)|Orbitals]], artificial rings built by the [[Forerunners]], an extinct technologically advanced race. The two known Halo installations, referred to as [[Alpha Halo]] and [[Delta Halo]] respectively, orbit [[Threshold|gas]] [[Substance|giants]], though it is not known whether this is the case of all the Halos, and Alpha Halo maintained an atmospheric mining facility until [[The Oracle (Level)|it was destroyed]] by the Covenant<ref>[[Halo 2]], [[The Oracle (Level)]]. </ref>Though separated by thousands of light-years, the seven installations are networked together and capable of remote activation at an [[Installation 00|Alderson Disk]] known as the Ark outside the galaxy. The array was designed by the Forerunners to eradicate sentient life from [[Milky Way Galaxy|the galaxy]], thereby denying the [[Flood]] a source with which to expand, and starving it to death to prevent its spread, and each Halo has a maximum effective range of 25,000 light-years.<ref>343 Guilty Spark: "Technically, this installation has a maximum effective range of 25,000 lightyears."</ref> The exact means the array uses to conduct this "mass sterilization protocol"<ref>Why naturally the Flood is simply too dangerous to release, and mass sterilization protocols may again need to be enacted.</ref> are unknown, though it is assumed to utilize energy in some form.It is possible that once the Index is reconnected with the Core, a dormant battery somewhere on the ring will activate and harness some sort of energy in the center of the ring. Once the energy reaches a mass suited for the range, the 3 phase pulse generators simultaneously release a pulse, possibly releasing the energy which will then lock onto and destroy all sentient life. '''''POSSIBLY'''''<ref>343 Guilty Spark: "Reclaimer, please understand that that interfering with the wave generation process will severely damage this installation.</ref>
Each of the Halo installations manufactured at Installation 00 is given a sequential designation number based on their order of construction, beginning from 01,{{Ref/Reuse|neoteric}} and is overseen by a single [[monitor]]. The monitors are given control of the Installations' [[Sentinel]] automatons, from [[Sentinel Aggressor|Aggressors]] to [[Constructor]]s and [[Enforcer]]s, and are responsible for containing the Flood test subjects in their [[Flood research facility|research facilities]] and protecting the Halo from intruders.


The Halo Array has been fired once in known history, approximately 100,000 years ago, by the [[Didact]]<ref>Iris Array Recorder Data </ref> in order to stop the [[Flood]] from overwhelming the galaxy. Despite being the networks builders, the Forerunners were killed in this last suicidal option to save the rest of the universe from a worse fate.<ref>343 Guilty Spark: "After exhausting every other strategic option, my creators activated the rings. They, and all additional sentient life in three radii of the galactic center, died, as planned."</ref> The array has nearly been activated twice since, [[Alpha Halo]] was almost activated by the [[Master Chief]] before being deactivated by [[Cortana]], while [[Delta Halo]] was activated by Commander [[Miranda Keyes]], forced by the [[Jiralhanae]] [[Chieftain]] [[Tartarus]], neither of which were successful. A [[Installation 04 (II)|replacement]] Halo for the destroyed Alpha Halo was activated outside of the array's range, eliminating the freed Flood, but did not activate the rest of the array.<ref>[[Halo 3]], [[Halo (Level)]]</ref>
The Array also encompasses [[Installation 00]], an extra-galactic construction facility that can create replacement installations in the event that one is destroyed. All Halos can also be remotely activated from the Ark without being subjected to their effects, as the megastructure is out of the Array's range.{{Ref/Level|Id=thecovenant|H3|[[The Covenant (level)|The Covenant]]|Quote='''343 Guilty Spark''': ''"The Ark is out of range of all the active installations!"''}} The Forerunners also built [[shield world]]s as a means to escape the effect without having to leave the galaxy.{{Ref/Novel|GoO|Page=??}}
{{clear}}


Each Halo Installation is given a designation number, from 01 to 07, and is overseen by a [[Monitor]]. The Monitors are given control of the Installations' [[Sentinels]], [[Constructors]] and [[Enforcers]], and are responsible for containing the [[Flood]] test subjects in their [[Flood Research Facility|research facilities]] and protecting the Halo from [[UNSC|intru]][[The Covenant|ders]].  
==History==
===Construction===
[[File:ForerunnerObserver.jpg|thumb|250px|A Forerunner observes the construction of a Halo.]]
The first Halos were constructed by the [[Master Builder]] [[Faber]] and his [[Builder]]s in the millennia after the [[Flood]] was first encountered in the Milky Way, only to eventually retreat, seemingly due to [[prehistoric human civilization|early humanity]]'s efforts. The most extreme faction of Builders, which at the time controlled the [[Ecumene Council]], claimed that more extreme measures should be used to protect the galaxy against a possible Flood resurgence and proposed building the Array for this purpose. The initial iterations of the weapon system that would eventually become Halo did not share the circular shape of the final installations.<ref>'''Halo: Cryptum''', ''page 243''</ref> Although they faced strong opposition from the [[Promethean]]s, led by the [[Ur-Didact|Didact]], for thousands of years, the faction eventually won the approval of the Council and commenced work on the Array.{{Ref/Reuse|c274}} Several prototypes of the Halos were constructed and powered by their host facilities, with [[Prototype Halo installation|one such installation]] orbiting a rogue planet.<ref name="SoI5">'''[[Halo: Shadow of Intent]]''', ''pages 5-10'' (Google Play edition)</ref>


The Array also encompasses an actual [[Wikipedia:Alderson Disk|Alderson Disk]], referred to as [[Installation 00|The Ark or Installation 00]], from which the array can be remotely and safely activated while out of firing range, and able to survive the effects<ref>343 Guilty Spark: The Ark is out of range! Of all the active installations!</ref>. The Forerunners also built active [[Shield World|Shield Worlds]], [[Wikipedia:Dyson Sphere|Micro-dyson Spheres]] encased in a slipspace field with their own star in the center and a habitable environment, as a means to escape the effect without having to leave the galaxy.<ref>[[Halo: Ghosts of Onyx]]</ref>
However, at this point, the [[Librarian]] went to the Council and invoked the Mantle, stating that the Halos should be used as biological preserves in the [[Conservation Measure]], a plan to repopulate the galaxy should the Array ever be activated. The Council approved her request, and ordered that the Halo installations be constructed to have a range of natural environments for the Lifeworkers to preserve their biological specimens in. The Builders also agreed, seeing the inclusion of biological preserves as an effective means of competing with the Didact's shield worlds which incorporated similar measures.<ref name="s44">'''Halo: Silentium''', ''page 44''</ref> However, the Master Builder later altered the initial plan, and his researchers began to use these specimens for a series of brutal experiments involving Flood infection.<ref>'''Halo: Primordium''', ''page 188-190''</ref>


== Features ==
Twelve Halos, each 30,000 kilometers in diameter, were originally commissioned by Master Builder Faber and constructed by [[Wise-Hands-to-Forge]]'s [[guild]] at the [[greater Ark]], the first Ark installation to be constructed. Only one of these original rings ultimately survived to be used in the Forerunners' final plan; this ring was designated [[Installation 07]]. Later on, an improved, separate array of six installations was constructed at the [[Installation 00|lesser Ark]],<ref>'''Halo: Cryptum''', ''page 329'' (''"Slowly it dawned on me that I was looking upon another array of installations: six rings, each rising from one of the petals of an enormous flower."'')</ref><ref name="s250">'''Halo: Silentium''', ''pages 250-251''</ref> although the construction of the second Ark and its more powerful Halos was delayed by the Council for some time to prevent the Builders from becoming too powerful.<ref>'''Halo: Silentium''', ''page 45''</ref>


=== Custodial ===
In the later stages of the construction of the first Halos, a Builder named [[Maker-of-Moons]] was assigned to improve upon their designs. The first test deployments had proven the original rings to be unstable and too large to be practically deployed, generating enormous [[Slipstream space#Reconciliation|particle reconciliation]] debt when moved. The original Ark also had several flaws, including the inability to construct smaller installations. Although initially reluctant to admit these defects,<ref name="maker">'''Halo: Silentium''', ''page 91''</ref> the Master Builder, informed by Maker's analysis, commissioned a new Ark and a series of new, more efficient rings several millennia after the first Halos were made; the Builders promoted this as a means to save even more species while being able to create more Halos. The new Ark, known as the lesser Ark or [[Installation 00]], and its six new Halos were constructed in secret,{{Ref/Reuse|s44}} their location known only to the Master Builder.<ref name="s270">'''Halo: Silentium''', ''page 270''</ref>
[[Image:343GS avatar.gif|right|thumb|343 Guilty Spark, Monitor of Installation 04]][[Image:POAEngineRoom.jpg|right|thumb|Sentinels combating the Flood]]
The installations are designed to be run by advanced Artificial Intelligence constructs specially purposed by the Forerunners. The highest Intelligence on each Installation is a single Monitor<ref>[[Halo: Combat Evolved]], level [[343 Guilty Spark (Level)|343 Guilty Spark]]</ref>. The Monitor's task is to ensure that the Installation's [[Constructors]], [[Sentinels]] and [[Enforcers]] repair, maintain and defend the ring from damage, contain the [[Flood]] specimens, and ensure that their own Installation is ready to fire on demand, including running activation simulations<ref>[[Halo 2]], [[Gravemind (Level)]], 2401 Penitent Tangent: This installation has a successful utilization record of 2.1 trillion simulated and one actual. It is ready to fire on demand.</ref>


In addition, each Installation contains less intelligent constructs, known as [[Sentinels]]. The [[Sentinels]] serve virtually any purpose necessary to ensure that the Halo functions properly; they are also capable of combating small Flood outbreaks. Should a major Flood outbreak occur, heavier automations, such as the [[Enforcers]] and [[Sentinel Majors]] will be created to assist the Sentinels. In the meantime, [[Constructors]] are also created to ensure that the Forerunner structures on the Installation are kept in optimal shape, and that they are not damaged by conflict or weather<ref>[[Halo 2]], level [[Sacred Icon (Level)|Sacred Icon]]</ref>.
The final Array, activated at the conclusion of the Forerunners' conflict with the Flood, comprised seven rings, each 10,000 kilometers in diameter, one of them being the reduced Installation 07.<ref name="s314">'''Halo: Silentium''', ''page 314''</ref>


Save for the Monitor, all automations can be constructed at specialized [[Sentinel Production Facility|Sentinel Production Facilities]] that float high in the Halo's atmosphere. These Facilities have never been seen (except briefly in the sky above the level [[Sacred Icon (Level)|Sacred Icon]], one can be seen crashing as you exit near the end of the level, you then fight through the remains of it in [[Quarantine Zone (Level)|Quarantine Zone]]), but they seem to contain limitless materials for constructing any number of automations.
===Forerunner-Flood war===
[[File:FoM.jpg|thumb|left|250px|The original Halos gathered in orbit around [[Maethrillian]].]]
The first test of a Halo installation was conducted by [[Mendicant Bias]], who fired [[Installation 07]] in [[Charum Hakkor system|the system]] of [[Charum Hakkor]] and [[Faun Hakkor]] on a low power setting, destroying all of the sentient life on the latter planet and inadvertently releasing the [[Primordial]], an extant [[Precursor]] entity, from captivity on the former planet. Mendicant Bias then brought the released being to the Halo for study and began a 43-year-long interrogation of it. Eventually, Mendicant Bias disappeared with Installation 07 after being [[logic plague|corrupted]] by the Primordial.


=== Environment ===
Following the use of a second Halo by Master Builder Faber to suppress [[Battle of Janjur Qom|a rebellion]] on the [[San'Shyuum]] homeworld of [[Janjur Qom]], the other eleven Halo installations were taken to the Forerunner [[Capital]] during the tribunal against Faber, where it was to be decided whether to decommission them. However, in the midst of the trial, Mendicant Bias, turned rampant by the Primordial, appeared with Installation 07, which had gone missing following the ancilla's corruption and [[Fate of Maethrillian|assaulted the Capital]]. The AI attempted to seize control of the remaining Halos and fire them, but was only able to control five out of the twelve. One of those five was destroyed by the combined tidal forces of the Capital, the firepower of local Forerunner fleets, and the stress of a recent [[slipspace]] transition. The seven Halos that Mendicant Bias was unable to control were recalled to Installation 00 via a [[slipspace portal]], yet only [[Omega Halo|one]] escaped before the portal collapsed, with the other six breaking up in slipspace.


The Halo installations were also designed to be habitable, and support a wide range of environments, habitats, ecosystems and climates. The two known installations, [[Alpha Halo|Alpha]] and [[Delta Halo]], both supported warm, temperate forests<ref>[[Halo (Halo: Combat Evolved Level)]]</ref><ref>[[Uprising (Level)]]</ref> that were both deciduous and coniferous, swamps, and cold, snow covered tundra environments<ref>[[Assault on the Control Room]]</ref><ref>[[Quarantine Zone (Level)]]</ref>. The Ark had climate ranging all the way from tundra<ref>[[The Covenant (Level)]]</ref>, to forest<ref>[[The Covenant (Level)]]</ref>,to desert,<ref>[[The Ark (Level)]]</ref>. It is unknown whether this range is shared by all Halo installations, but the similarity of these environments and that of [[Installation 00]] makes it likely. However, if one observes the holograms of the installations after stopping the Ark, one will see that the rings have different surface features and may have different atmospheres as well.
Installation 07 jumped into a distant system on a pre-designated destructive collision course with [[Wolf-faced planet|a planet]]—a security measure put in place in the event that it fell out of Forerunner control. The installation was eventually reclaimed by the IsoDidact's forces, and it survived the passage of the planet despite taking heavy damage. A significant amount of the ring's superstructure was discarded, reducing its size to 10,000 kilometers, in order to allow it to perform a successful slipspace jump to the [[greater Ark]]. The installation's surviving biological specimens were transported on the Ark and the Flood outbreak on the ring was contained. The ring was refitted to enable it to function in concert with the six final Halos and deployed to its final station in the galaxy; the distribution of the final Halo Array would follow several years later.{{Ref/Reuse|s314}}


While the terrain may appear to be naturally formed at first glance, it is actually artificially transformed by the [[Constructor]] and [[Sentinel]] constructs. An intricate layer of metallic panels is laid down several meters below the surface of the terrain, upon which rock, soil, and eventually vegetation is added. Slopes, hills and mountains can be created by sculpting these panels<ref>[[Halo (Halo 3 Level)</ref>. Some features, such as landslides, are the result of time, and have been formed naturally. Others, such as the myriad network of tunnels and cave systems that riddle the Installations internal structure, are travel conduits used by the rings [[Sentinels]] and [[Enforcers]]. There also some life-forms that live naturally on the Halos. Whether these were created by the Forerunners or were brought to the Halos by them is unknown.
During the battle at the Capital and the years that followed, all but one of the original twelve rings—[[Omega Halo]]—apart from the repurposed Installation 07 were hunted down and destroyed by the Flood.<ref>'''Halo: Silentium''', ''pages 234, 237''</ref> In the final hours of the Forerunner-Flood war, the ecumene's leadership retreated to the greater Ark, also home to Omega Halo. When a [[Battle of the greater Ark|Flood attack]] became imminent, it was decided that the IsoDidact go to the lesser Ark where he would deploy and fire the final Halo Array. Before relinquishing the coordinates to his secret Ark,{{Ref/Reuse|s270}} the Master Builder met the IsoDidact in the control room of Omega Halo and fired the ring, obliterating a small portion of the [[star road]]s laying siege on the Ark and cleansing the [[Large Magellanic Cloud]] of life.<ref name="s273">'''Halo: Silentium''', ''page 273''</ref>


=== Technology ===
====Activation====
[[Image:Control Room2.jpg|thumb|right|Control Room of Installation 04]]
{{Main|Great Purification}}
Each Halo has several assets that are conditional to all Installations. Each contains a [[Control Room]] located somewhere upon its inner surface, from which a Reclaimer must manually insert the Installations [[Index]] to activate it. Each also possesses a [[Library]], a large structure protected by an energy shield, where the Index is housed and protected by [[Sentinels]]<ref>[[The Library (Level)</ref><ref>[[Sacred Icon (Level)]]</ref>. The index itself is a semi-solid holographic representation of the data needed to activate the ring, and can only be inserted successfully by a [[Reclaimer]].
[[File:Array.png|thumb|300px|Installation 00 sending the Halo Array through a [[slipspace portal]] during the [[Forerunner-Flood war]].]]
The Flood and the star roads destroyed both Omega Halo and the greater Ark, but the IsoDidact managed to escape to Installation 00 to fulfill his mission. Arriving at the lesser Ark, the IsoDidact had the rings' Index collection distributed to their respective installations aboard a Lifeworker vessel over the Ark. The installations' primary monitors were also formally given their assignments to their final posts. Each monitor received a new name and numeric designation, each intended to serve as a form of memorial to the Forerunners.<ref>'''Halo: Silentium''', ''page 313''</ref> With the assistance of [[Offensive Bias]], the IsoDidact deployed the remaining six Halos from [[Installation 00 Citadel|the Ark's Citadel]]. Together with Installation 07, these installations comprised the final Halo Array of seven rings.{{Ref/Reuse|s314}}


Installations also possess [[Silent Cartographer|Cartographer]] facilities, holographic representations of the Installations inner passages and networks, to be used as a navigational reference for exploring the Installation. [[Flood Containment Facilities]] are also standard, used by the Installations Monitor to conduct research on and observe the surviving [[Flood]] specimens, also protected by [[Sentinels]] to prevent outbreak.<ref>[[Halo: The Flood]] page 240</ref>
[[File:HaloFiring.png|thumb|left|250px|The Halo Array fires, ending the conflict.]]
As Mendicant Bias and the Flood prepared their [[Battle of the Maginot Sphere|final assault]] on the lesser Ark in order to stop the firing of the Halos, the IsoDidact activated the Array. [[Installation 04]] was first in the Array to fire, with the others following sequentially as their fields intersected.<ref name="sil326">'''Halo: Silentium''', ''pages 326-327''</ref> The pulse covered the entire galaxy, killing all sentient life within range and destroying the Precursors' [[neural physics]] architecture, including the [[Domain]] the Forerunners used to hold dear.<ref>'''Halo: Silentium''', ''pages 322-323''</ref> Whether the pulse would destroy star roads and other Precursor artifacts in faster-than-light transit was uncertain even to the Forerunners themselves, due to the largely unknown mechanisms of Precursor superluminal travel.<ref name="s312">'''Halo: Silentium''', ''page 312''</ref> However, their total destruction seems apparent from the fact they were no longer in evidence when the Forerunners repopulated the galaxy.{{Ref/Reuse|rebirth}}


Installations also contain advanced [[Teleportation Grid|teleportation grids]], allowing instantaneous transportation for a Monitor or Reclaimer to any place on the Installation. These grids can not be controlled by the [[Flood]] but the Gravemind is able to use it by controlling 2401 Penitant Tangent<ref>[[Gravemind (Level)]]</ref>. For regular Sentinels, the Installation is riddled with tunnel and cave networks for access and transportation<ref>[[Halo: The Flood]], page 242.</ref>.
It was later discovered that a species called the [[Xalanyn]] had somehow survived the firing of the Halo Array. Frightened that the Xalanyn would eventually become the dominant species of the galaxy and claim the [[Mantle of Responsibility]], the Forerunners brought [[Installation 07]] into orbit of the Xalanyn homeworld under the pretense of a meeting and imprisoned them on the ring for containment and study.{{Ref/Game|Hi|Detail=[[Audio log (Halo Infinite)|Audio logs]]}}


== Function ==
===Post-activation===
[[Image:Installation 05.jpg|200px|thumb|right|The [[Forerunner]]'s structure [[Installation 05]], otherwise known as '''Delta Halo''', misfiring, after which it sent a standby signal to the other installations.]]
The seven Halos then remained relatively dormant for approximately 100,000 years, though at least [[Installation 05]] experienced a major Flood outbreak, while [[Installation 04]] was visited briefly by other species,<ref>''"[[Conversations from the Universe]]"''</ref> including a [[unidentified alien vessel|major crash-landing]] in [[40,000 BCE]].<ref>'''Halo: Combat Evolved Anniversary''', ''[[Terminal (Halo: Combat Evolved Anniversary)|Terminals 5-6]]''</ref>


The Halo Array is complex, but each can be activated individually by a [[Reclaimer]], also activating the other Installations, or they can all be activated simultaneously from [[Installation 00|The Ark]]. In the event of a major [[Flood]] outbreak, the Installations Monitor will seek out a Reclaimer if available, who they will enlist to aid them. It will teleport them to the Installation's [[Library]], and assist the individual in retrieving the Index, needed to activate the Installation. The Monitor then stores the Index within its data arrays for safe transportation, lest the Reclaimer fall prey to the [[Flood]] before they can activate the Installation. Once at the [[Control Room]], the Reclaimer must insert the Index into the control panel in order the begin the activation sequence.
The Array's activation caused catastrophic damage to ecosystems across the galaxy, with innumerable species both sentient and non-sentient rendered extinct. The dissolving of dead bodies thanks to [[solute]] eventually showed up on the fossil record, and was labeled by scientists as the [[Ross-Ziegler Blip]]. This curious gap was dismissed as an anomaly caused by spatial distortion until [[human]]ity discovered the Array in [[2552]]. Several species indexed by the [[Library Project]] did not survive [[reintroduction]] to their homeworlds, and those that did were all reverted to a [[Technological Achievement Tiers#Tier 7: Pre-Industrial|Tier 7]] technological state. The mostly uneventful period starting after the firing of the Halos was known as the [[dark time]].


The main weapon is amplified by a trio of [[Phase Pulse Generators|phased pulse generators]] built close to the Control Room. It is unknown exactly what means the Halo Array employs to kill sentient lifeforms over non-sentient life. A common misconception is that it kills the Flood, however this is untrue as it kills all sentient beings as resource-denial to the Flood. Each Installation has a maximum effective radius of 25,000 light-years<ref>[[Halo: Combat Evolved]], [[Two Betrayals (Level)]]</ref>, and is apparently of the "Highest possible threat assessment from biological contamination and radiological annihilation"<ref>[[Halo: Ghosts of Onyx]]</ref>. The pulse is designed to kill all sentient life in the Installations three-dimensional radius, with the entire array covering the entire galaxy. The only known way to avoid the effects of these pulses is to escape to a [[Shield World]], located in slip-space and therefore immune from its effects, or to escape to [[Installation 00]], which is out of range.
The [[Covenant]], a theocratic multispecies alliance, was founded on the misguided belief that the Halo Array was actually the source of a "Divine Wind" that allowed the Forerunners to transcend the physical. By activating the Array, they too could embark on this "[[Covenant religion|Great Journey]]" and join the Forerunners in godhood.


*The explosion seems reminiscent of an implosion followed by a rapid explosion.
===Rediscovery===
[[File:H2A-AlphaHaloDestruction.jpg|250px|thumb|The destruction of Installation 04.]]
Eventually, the stellar coordinates of [[Installation 04]] were discovered through the combination of a [[Sigma Octanus IV artifact|crystal artifact]] on [[Sigma Octanus IV]] and a [[Babd Catha Forerunner vessel|huge Forerunner artifact]] buried under the surface of [[Reach]]. The coordinates were utilized by the {{UNSCShip|Pillar of Autumn}}'s shipboard [[AI]] [[Cortana]] to escape from the [[Fall of Reach]]. The cruiser arrived over the Installation's orbit and was subsequently shot down by Covenant ships. Most of the ship's combat personnel escaped and made landfall on the artificial construct, triggering the [[Battle of Installation 04]].


== History ==
During their investigations on Installation 04, the Covenant encountered a [[Flood containment facility]] and unknowingly released the dormant Flood; they quickly, but only partially, reestablished containment. Soon, a squad of [[UNSC Marine Corps|Marines]] led by [[Captain (Navy)|Captain]] [[Jacob Keyes]] accidentally broke quarantine again, expecting to find a large Covenant weapons cache. The human-waged guerrilla war quickly turned into a massive four-way battle between [[United Nations Space Command|UNSC]] forces, the Covenant, [[Sentinel]]s led by [[343 Guilty Spark]], and the Flood.
[[Image:AlphaHaloview2.jpg|right|thumb|The destruction of Installation 04]]
The Halos were constructed by the Forerunners a few hundred years ''after'' the Flood was discovered by the ''Array's'' makers, because their builders saw that their current isolation and containment procedures were not adequate to stop the spread of the Flood. Little is known of their extensive history, (At least one was functional for 101,217 Local years)<ref>[[Halo: The Flood]] page 238</ref> but after exhausting every other tactical option, their creators had no choice but to activate the Halos' main weapon, and terminate all sentient life in the galaxy<ref>[[Halo 2]], level [[The Great Journey]]</ref>.
It is possible, and implied, that the Halo rings were not used in conjunction with the [[Key of Osanalan]], causing the Halos failure to completely obliterate the Flood.


The seven Halos then remained relatively dormant for one hundred thousand years (Though at least one of them experienced a major Flood outbreak; and reference given to brief visits by other species by 343 Guilty Spark) until one of them, Installation 04 (known amongst fans as Alpha Halo), was discovered by the theocratic alien superpower, the Covenant. The Covenant, who revered the Forerunner as gods, believed that the Halo's main weapon was actually a source of "divine wind" meant to propel them on a path they called the "[[Great Journey]]". During their investigations on Installation 04, the Covenant encountered the Flood, however they quickly, but only partially contained the outbreak. After the arrival of the [[Human]] vessel ''[[UNSC Pillar of Autumn]]'', [[Captain]] [[Jacob Keyes]] accidentally breaks the containment, thinking to find a large Covenant weapons cache. A massive four way melee ensued between the Covenant, the 343 Guilty Spark-led Sentinels, the Flood, and the Humans. This finally culminated when the Human Super-soldier known as the [[Master Chief]] detonated the fusion engines of the ''Pillar of Autumn'' on the surface of the Installation, compromised the structural integrity of the ring, and, due to the gravitational momentum and inertia still perpetuating the ring in orbit around [[Threshold]], tore the ring apart into pieces. The remains of installation 04 are scattered as debris in space, both large and small. The explosion sent massive chunks of the ring careening into the moon [[Basis]], as seen in the [[Halo 2]] Multi-Player Level "[[Burial Mounds (Level)|Burial Mounds]]," due to the constant bombardment of small objects from the ring as seen in the sky on that map. Other large sections of the ring are seen in the opening scene of Halo 2, drifting in space around Threshold. It is also highly likely that large portions of Alpha Halo debris were drawn into Threshold, never to be seen again. <ref>[[Halo: Combat Evolved]], level [[The Maw]]</ref>.
[[File:Halo Firing.png|250px|left|thumb|The partially constructed Installation 08 hovering over the Ark.]]
The battle finally culminated when [[SPARTAN-II program|Spartan]] [[John-117]] detonated the [[fusion engine]]s of the ''Pillar of Autumn'' on the surface of the installation, which compromised the structural integrity of the ring. The gravitational momentum and inertia still perpetuating the ring in orbit around [[Threshold]] then tore the ring apart. The remains of Installation 04 were scattered as debris in space. The explosion sent massive chunks of the ring careening into [[Basis]]; the moon suffered a constant bombardment of debris from the ring after its destruction.<ref>'''Halo 2''', multiplayer level ''[[Burial Mounds]]''</ref>


Later, a second Halo, Installation 05 (known amongst fans as Delta Halo), was discovered. On this Halo, the Flood had already been released somehow. And owing to this, a similar conflict erupted. This conflict ended in the Flood manifesting a [[Gravemind]] and successfully escaping the ring aboard infected [[Covenant]] ships. The ring was nearly activated by [[Tartarus]], a [[Brute Chieftain]], but [[Commander]] [[Miranda Keyes]] pulled the [[Index]] out of the Installation at the last moment, causing the six remaining Installations to go on "standby mode", ready for remote activation from the Ark.
After escaping the [[Battle of Tribute]], a UNSC [[freighter]], ''[[Floral Express]]'', discovered [[Installation 03]] on October 8, 2552. By October 25 neutralization protocols had been established.<ref>''[[Eleventh Hour reports]]'' - ''#5''</ref>


The Humans return to [[Earth]] and resume their fight against the Covenant, who have uncovered a large structure on Earth, which they assume to be the Ark. The Covenant set the [[Forerunner Dreadnought]] down in the center of the structure, activating it. To everyone's surprise, the structure is not the Ark, but a portal to the Ark, a massive artificial world located outside the galaxy. Human and [[Elite]] forces go to the Ark to try and stop the Covenant from activating the Ark, thus activating the remaining Halo rings. It is then that the [[Flood]] [[Gravemind]] appears, having turned the Covenant planetoid city ''[[High Charity]]'' into a Flood hive. The Hive crashes on the Ark, releasing the Flood.  
Later, the Covenant discovered a third Halo, [[Installation 05]]. On this Halo, the Flood had already been released and much of the ring had been compromised, including its monitor, [[2401 Penitent Tangent]]. Soon, [[Battle of Installation 05|another four-way conflict]] began. The battle ended in the Flood manifesting a [[Gravemind]] and successfully escaping the ring aboard the infected {{UNSCShip|In Amber Clad}}. The ring was nearly activated by [[Tartarus]], the [[Chieftain of the Jiralhanae|Chieftain]] of the [[Jiralhanae]], but [[Commander]] [[Miranda Keyes]] pulled the [[Activation Index]] out of the installation's core at the last moment, causing all six functional installations to go into "standby mode", ready for remote activation from the Ark.


It is revealed at this point that the Ark was constructing a new Installation 04, to replace the one destroyed, that is only days from being complete. The Humans eventually decide to activate the new ring to stop the Flood, which in turn destroys itself and damages the Ark. It is unclear how the system was affected by this, but the Halo system appears to have been irreparably damaged by the destruction of Installation 04, its [[Monitor]]([[343 Guilty Spark]]), and the heavy damage done to the Ark.
The human survivors returned to [[Earth]] and resumed their fight against the Covenant, who had uncovered a large structure on Earth, which they assumed to be the Ark. The Covenant landed the [[keyship]] ''[[Anodyne Spirit]]'' in the center of the structure, activating it. However, the structure was soon revealed not to be the Ark, but [[the Portal|a generator]] of a portal to the actual [[Installation 00|Ark]], a massive artificial world located outside the galaxy. Human and [[Swords of Sanghelios|Sangheili]] forces proceeded through the portal to the newly-discovered installation to prevent the Covenant from activating the remaining Halo rings remotely. Eventually, the Gravemind arrived at the Ark aboard [[High Charity]], the Covenant's capital city, which had been turned into a Flood hive. The hive crashed onto the installation, releasing the Flood.


==Astronomy==
Soon, 343 Guilty Spark, John-117, and [[Arbiter]] [[Thel 'Vadam]] discovered that the Ark had been constructing a [[Installation 08|new Installation 04]], to replace the one which had previously been destroyed. This new installation was only days from being completed. The humans decided to activate the new ring to stop the Flood, resulting in the incomplete ring destroying itself,<ref>'''[[Halo: The Essential Visual Guide]]''', ''page 14''</ref> severely damaging the Ark in the process.<ref name="hitd c2">'''Halo: Hunters in the Dark''', Chapter 2</ref>
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[[Image:Lagrange Point.png|300px|right]]
The "Ringworld" of Halo is much smaller than [[Wikipedia:Larry Niven|Larry Niven's]] [[Wikipedia:Ringworld|Ringworld]]. While the diameter of Niven's ring world is close to the diameter of Earth's orbital of 300,000,000 km, the 10,000 km diameter of Halo is much closer to the diameter of Earth itself, which is 12,756 km. Ringworld has a star similar to our sun in its center, and Halo is orbiting a planet, but does not encircle it.


Besides the very beautifully sculpted landscape on Halos surface, the sky is also worthy of attention. Depending on the viewpoint, you can see a star, a moon (called [[Basis]]), a gas giant (called [[Threshold]]), and the band of Halo itself, which looks like a street into the sky.
===Post-Covenant War===
[[File:HSS-Infinity-Halo.png|thumb|250px|The {{UNSCShip|Infinity}} approaches Installation 03.]]
By [[2553#January|January 2553]], the UNSC had begun an active search for the remaining Halo installations, with the intent to decommission them.<ref>'''Halo: Glasslands''', ''page 50''</ref> By at least [[2557|July 2557]], UNSC scientists were studying the Array for decommissioning, with facilities at Installations 03 and 05. Installation 00 was scouted by both automated probes and the ONI vessel {{UNSCShip|Rubicon}}, which was lost several days after its arrival due to the actions of [[343 Guilty Spark]].{{Ref/Novel|Pri}}
 
[[Installation 07]] was discovered in early [[2555]] due to records found on [[Sarcophagus]] by Dr. [[Luther Mann]] with an ONI research group stationed on the ring immediately afterward. A crisis occurred when it was discovered that Installation 07 — as well as the other Halos — were counting down to activation in five weeks from March 8, 2555. As the stand-by failsafe protocol had never been deactivated, it was realized that the Ark was the only location where the Array could've been activated. With the help of [[Huragok]] [[Drifts Randomly]], the [[Portal at Voi]] was reactivated, but Earth came [[Invasion of Earth|under attack]] from [[Retriever Sentinel]]s from the Ark. A joint UNSC-[[Swords of Sanghelios]] [[Operation: FAR STORM|mission]] was launched to the Ark where it was discovered that the Ark's now-[[rampancy|rampant]] [[monitor]], [[000 Tragic Solitude]], had initiated the activation with the help of [[Bobby Kodiak]]. Having witnessed the destruction sentient life caused, particularly to Forerunner constructs, Tragic Solitude had activated the Array for a two-fold reason: to trick humanity into reactivating the portal so he could strip-mine Earth for materials to repair the Ark and eliminate the sentient species of the galaxy. Mann was able to deactivate the Array from the Ark and the team forced Tragic Solitude to end the Invasion of Earth. After Tragic Solitude attacked again, he was destroyed by Bobby Kodiak at the cost of his own life, ending the threat the rogue monitor posed to sentient life.{{Ref/Novel|HitD}} At some point following the loss of Installation 08, Installation 00 began to construct [[Installation 09|a new replacement]], one that would be maintained in the Ark's Foundry in a near-finished state for some time.{{Ref/Level|Id=Hold the Line|HW2|[[Hold the Line]]}}
 
In [[2556#February|February 2556]], the [[Outer Colony]] world of [[Sedra]] suffered a deadly [[bioweapon]] [[Terrorist attack on Sedra City|attack]] by [[Unidentified Sangheili Zealot (Sedra)|a Sangheili terrorist]]. The bioweapon source was traced to a new element mined from [[Alpha Shard|a surviving fragment]] of [[Installation 04]], created by the [[supernova]]-level explosion that had destroyed the original installation. A joint [[ONI]]-[[Sedran Colonial Guard]] [[Mission to Alpha Shard|mission]] was launched to capture the human smugglers mining the element and to destroy the deposits to prevent future use of the bioweapon. Though most of the team was killed, ONI [[Lieutenant Commander]] [[Jameson Locke]] and Sedran Private [[Talitha Macer]] escaped in the smugglers' {{Class|Bactrian|freighter}} while [[Colonel]] [[Randall Aiken]] sacrificed himself to destroy the deposits and the fragment's resident [[Lekgolo]] population with a [[HAVOK tactical nuclear weapon]].{{Ref/Film|HN}}
 
By early [[2557]], humanity had returned to the Ark and set up the [[Henry Lamb Research Outpost]]. Under the guidance of the [[smart AI]] [[Isabel]], the researchers began directing Retriever Sentinels to strip-mine lifeless systems to repair the Ark. The reconstruction slowly reached full automation until the humans were no longer needed to nudge it along. Over time, the Ark was repaired with noticeable differences between one day and the next over only the course of three months.{{Ref/Game|HW|Detail=''[[Phoenix Logs]]''}}
 
Later, the scientists studying Installation 03 located the [[Composer]] on the ring and accidentally activated it, causing them to [[mind transfer|become digitized]]. However, the sensor data left over from the incident led to the discovery of the [[shield world]] [[Requiem]]. Later, the [[Ur-Didact|Didact]] traveled to Ivanoff Station near Installation 03 to retrieve the Composer and used the device to harvest the essences of the entire research staff before heading for Earth.{{Ref/Game|H4}} Meanwhile, [[Jul 'Mdama's Covenant]] and their [[Promethean]] allies attempted to take control of Installation 03 by using the [[Conduit]] to open [[slipspace portal]]s across the ring, but the attack was repelled by a [[Spartan]] [[Headhunter]].{{Ref/Level|SS|[[Operation C: Valiant Hammer]]}}
 
[[File:HW2 I04C.png|thumb|250px|left|The [[Installation 09|second replacement Halo]] above the Ark in [[2559]].]]
A day later, after the Didact's [[New Phoenix Incident|defeat at Earth]], the Forerunner and some of his Promethean forces fell on Installation 03 via a slipspace portal. SPARTAN-II [[Blue Team]] followed, resulting in a [[Mission to Installation 03|skirmish]] fought on both Installation 03 and the [[Composer's Forge]]. The Forge's monitor, [[859 Static Carillon]], transported Installation 03 over the Forge for the Didact, who intended to use the ring to finally destroy humanity.{{Ref/Comic|Id=HE9|HE|Detail=''[[Halo: Escalation Issue 9|Issue 9]]''}} However, the monitor instead allied with the Spartans due to his disagreements with the Didact and helped them defeat the Forerunner. After John-117 disabled the Halo's failsafes, Static Carillon ejected the segment housing the [[Control Room (Installation 03)|control room]], causing it to fall upon the Composer's Forge. The monitor then stabilized the ring and took it to an unknown location for repairs.{{Ref/Comic|Id=HE10|HE|Detail=''[[Halo: Escalation Issue 10|Issue 10]]''}}
 
In late [[2558]], Installation 00 became a battlefield once again as the mercenary organization known as the [[Banished]] arrived there following a sudden shutdown of the Earth portal. The Banished launched an assault on the UNSC bases on the Ark and soon gained control of the entire installation. In [[2559|May 2559]], the {{UNSCShip|Spirit of Fire}}, having drifted in space for 28 years, was mysteriously transported to Installation 00 by an agency evidently within the Ark.{{Ref/Level|HW2|[[The Signal]]}} During [[Second Ark Conflict|the ensuing conflict]] between the UNSC and the occupying Banished forces, Professor [[Ellen Anders]] learned of the contingency ring held within the Foundry and was able to launch the new Halo, with the intent of deploying it to Installation 04's former site in the [[Soell system]] where a [[distress beacon]] could be raised to the UNSC.{{Ref/Reuse|Hold the Line}} While the Halo was successfully sent through the portal, its firing mechanism disabled by Professor Anders, the ring was intercepted and forced out of slipspace on the way by a [[Guardian]].{{Ref/Level|Id=Last Stand|HW2|[[Last Stand (Halo Wars 2 level)|Last Stand]]}}
 
In October 2559, the Banished succeeded in opening a slipspace portal to [[Reach]] through which Atriox and some of his forces returned to the Milky Way galaxy in [[Pegoras|a]] [[Eklon'Dal Workshop Lich]]. Before the portal was shut down, [[Castor]] and his small detachment of the [[Keepers of the One Freedom]] hijacked Atriox's Lich and used it to fly back through the portal to the Ark, intending on using the Ark to fire the Halo Array and start the Great Journey.{{Ref/Novel|Id=SoR|SoR}}{{Ref/Book|Id=Enc22P247|Enc22|Page=247}} On the Ark, the Keepers allied themselves with [[Prelate]] [[Dhas Bhasvod]] and his [[Dhas Bhasvod's Covenant]], guided by the Forerunner [[archeon-class ancilla]] [[Intrepid Eye]] who sought to fire the Halo Array in order to destroy the [[Domain]] and defeat [[Cortana]] for the sake of her own plans. The combined factions were opposed by both forces from the ''Spirit of Fire'' and the Banished spearheaded by the [[Clan of the Long Shields]] as neither the Banished nor the UNSC wanted Castor and Bhasvod to succeed. The Covenant and Keeper forces were able to reach [[Epsilon Clarion]], the only facility on the Ark capable of firing the Halo Array that was not inaccessible or inoperable. However, they suffered heavy casualties from UNSC and Banished [[Battle of Epsilon Clarion|attacks]] along the way and Castor abandoned his plans after learning the truth about the true purpose of Halo. On the order of [[Veta Lopis]], the ''Spirit of Fire'' launched an [[orbital bombardment]] of [[EMP]] [[MAC]] rounds that destroyed Epsilon Clarion and with it, Intrepid Eye and the Ark's ability to fire the Array. The Keeper detachment was left decimated with only Castor and Sangheili [[Blademaster]] [[Inslaan 'Gadogai]] surviving while Bhasvod, after killing [[Mark-G313]], departed to link up with the rest of his own forces.{{Ref/Novel|Id=DW|DW}}
 
In [[2559#December|December 2559]], the Banished took over Installation 07 in search of the [[Xalanyn]] who had been imprisoned on the ring following the [[Great Purification]]. When the UNSC came to the ring in order to stop [[Cortana]] once and for all, [[Battle for Zeta Halo|a conflict]] erupted on the ring between the two sides, leading to the apparent destruction of the ''Infinity''. In [[2560#May|May 2560]], the [[Harbinger]] succeeded in locating her species just before the Master Chief killed her. Subsequently, Atriox reached and unlocked a facility on Zeta Halo holding the [[cylix]]es of the Xalanyn. During the destruction event that shattered a portion of the ring at the hands of Cortana, Installation 07 itself was moved from the Ephsu system to an unknown location{{Ref/Game|Id=OI09|Halo Infinite|Database|Detail=Outpost Intel 09 - To Andrew Valleros}}{{Ref/Novel|RP|4}} by Cortana.{{Ref/Novel|Id=RP30|RP|30}} [[Lieutenant]] [[TJ Murphy]] speculated that it could've been moved clear across the galaxy or even into [[intergalactic space]].{{Ref/Novel|RP|Id=RP13|13}}{{Ref/Game|Hi}}
 
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==Features==
[[File:LoreStream Halo Scale Comparison.png|left|thumb|250px|The scale of the UNSC ''Infinity'' and Mt. Rainier when compared to a Halo Ring.]]
===Structure===
[[File:HaloLatticework.jpg|thumb|250px|The foundational latticework of a Halo installation.]]
The Halos encountered in the modern times are 10,000 kilometers in diameter; this size is roughly similar to that of [[Earth]], which is 12,756&nbsp;km in diameter. While the original twelve Halos had a diameter of 30,000 kilometers,<ref>'''Halo: Cryptum''', ''page 310''</ref> concerns about their structural stability and transport led to the second series of rings being reduced in size.{{Ref/Reuse|maker}} The surface of each ring is 318 kilometers wide,<ref>'''Halo: The Essential Visual Guide''', ''page 6''</ref> with a depth of 22.3 kilometers<ref>'''Halo: The Fall of Reach''', ''page 339'' (2001)</ref><ref>'''Halo: The Flood''', ''page 13'' (2003)</ref> to 47 kilometers.{{Ref/Reuse|Lorestream}}{{Ref/Note|The depth laid out in ''Halo: The Fall of Reach'' lists the ring's thickness as 22.3km, while the Lore Stream conducted by 343 Industries lists a depth of 47km. It is possible this disrepancy comes from the inclusion (or lack thereof) of the outer walls keeping the atmosphere in.}} The overall circumference of the ring is 31,415&nbsp;km and the interior surface area is 9,985,200&nbsp;km<sup>2</sup> - roughly the size of Canada.{{Ref/Reuse|Lorestream}} The main structure of the ring is constructed of a superdense foundational material,<ref>'''Halo: The Flood''', ''page 340''</ref> with elaborate scaffolding and cantilever structures laid over it to support the artificial landmasses and the myriad tunnel networks and caverns that riddle the installation's internal structure.{{Ref/Level|Id=halo3halo|H3|Halo_(Halo_3_level)}} Many of these tunnels are transit conduits meant for use by the ring's Sentinels, though some of them can be traversed by humanoid beings.<ref>'''[[Halo: Combat Evolved]]''', campaign level ''[[Halo (Halo: Combat Evolved level)|Halo]]''</ref>
 
The Halo rings achieve their "gravity" through [[artificial gravity]] generators - despite their shape, the ring does not need to spin to create its gravitational pull, though they do spin for other reasons unrelated to gravity generation.{{Ref/Reuse|Lorestream}} Due to this, the various [[Refugia]] present on the installation's surface may have different surface gravity, terrain, lighting and atmospheric conditions. These refugia are very modular and reconfigurable to support various types of life that are seeded on the rings.{{Ref/Reuse|Lorestream}} When the {{UNSCShip|Pillar of Autumn}} was detonated, it blasted a large mass from Installation 04; no longer a full loop, the centripetal force applied in much greater strength on the newly formed weak point, causing the ring to rip apart.<ref>'''Halo: Combat Evolved''' campaign level, ''[[The Maw]]''</ref>
 
[[File:HW2-Banished ejected.png|thumb|left|250px|A section of landmass being ejected from [[Installation 09]].]]
The Halos are capable of repairing themselves to some degree, replacing damaged plates of foundation material and restoring biological sections.<ref>'''Halo: Primordium''', ''page 77-78''</ref> Some of the 30,000&nbsp;km-diameter Halos could also be reduced to a smaller size by shedding large portions of the foundation.{{Ref/Reuse|maker}} In order to prevent the ring from falling apart during this process, it could generate a hard light hub with spokes which hold each of the foundation plates in place.<ref>'''Halo: Primordium''', ''pages 345-346''</ref> However, the self-reduction process was far from perfect and made the original Halos prone to instability and collapse.{{Ref/Reuse|maker}} The newer Halos are capable of safely ejecting segments as well due to their modular and reconfigurable construction,{{Ref/Reuse|Lorestream}} as long as the process is overseen by a capable enough intelligence such as a [[monitor]].{{Ref/Reuse|HE10}} Additionally, small, specifically defined parts of the Halos' terrain (along with the underlying foundation layers) can be jettisoned into space as a precautionary measure against Flood outbreaks.{{Ref/Reuse|Last Stand}}<ref name="cea t4">'''Halo: Combat Evolved Anniversary''', ''[[Terminal (Halo: Combat Evolved Anniversary)|Terminal Four]]''</ref> In time, the ecosystems of these ejected sections can be restored by the Halos' automated systems.{{Ref/Reuse|cea t4}}
 
Halos also possess [[hard light]] reinforcement to stabilize and protect them against tidal and gravitational forces from other objects.<ref>'''Halo: Cryptum''', ''page 311''</ref> One of the most extraordinary systems possessed by the Halos (at least the twelve original rings) is their ability to lock entire sections of the ring, or, if necessary, the entirety of it, into [[Slipspace bubble|reflective slipspace stasis]]. This suspends these sections in time and renders them invulnerable to damage from the outside, but consumes an enormous amount of energy.<ref>'''Halo: Primordium''', ''page 331-332''</ref>
 
Each installation in the final Halo Array orbits a large, dense planet—most commonly a gas giant—which serves as a gravitational anchor.{{Ref/Reuse|gas giants}}{{Ref/Reuse|Lorestream}} For example, Installation 04 and Installation 05 orbited [[Threshold]] and [[Substance]], respectively, which are both large gas giants, while Installation 03 is anchored to a large rocky planet.{{Ref/Reuse|h4composer}}
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===Custodial===
[[File:343.JPG|thumb|250px|343 Guilty Spark, monitor of Installation 04.]]
The installations are designed to be run by advanced artificial intelligence constructs specially assigned by the Forerunners. The highest intelligence on each installation is a single monitor.<ref>'''Halo: Combat Evolved''', level ''[[343 Guilty Spark (level)|343 Guilty Spark]]''</ref> The monitor's task is to ensure that the installation's [[Sentinel]]s, which range from [[Constructor]]s to [[Sentinel Aggressor|Aggressors]] and [[Enforcer]]s, repair, maintain, and defend the ring from damage, contain Flood specimens, and ensure that their own installation is ready to fire on demand, including running activation simulations.{{Ref/Reuse|gravemind}} In the event that a Halo Ring is destroyed, Tragic Solitude, Custodian of Installation 00 had the authority to assign a monitor to a ring. However, because Tragic Solitude was destroyed, Installation 09 was not assigned a monitor to oversee it.{{Ref/Reuse|Lorestream}} Monitors also have access to their respective installation's defensive system.<ref>'''Halo: Combat Evolved Anniversary''', ''Terminal 1''</ref> Monitors are also permitted to make alterations to the Halo ring, as seen with 343 Guilty Spark ejecting sections of the ring during his time on Installation 04, as long as they do not interfere with primary functions of firing the Halo. Another instance of alterations made was with Installation 08, which would not be identical in every physical characteristic to Installation 04, as 343 Guilty Spark had made modifications and changes to the ring prior to its activation.{{Ref/Reuse|Lorestream}}
 
The Sentinels encompass a broad category of less intelligent constructs which serve virtually any purpose necessary to ensure that the Halo functions properly and are capable of combating small Flood outbreaks. Should a major Flood outbreak occur, heavier automatons, such as the Enforcers and [[Sentinel Major]]s will be created. In the meantime, Constructors are also created to ensure that the Forerunner structures on the Installation are kept in optimal shape, and that they are not damaged by conflict or weather.<ref name="Icon">'''Halo 2''', level ''[[Sacred Icon]]''</ref>
 
Save for the monitor, all automatons can be constructed at specialized [[Sentinel manufacturing facility|production facilities]] that float high in the Halo's atmosphere. They seem to have access to copious amounts of materials for constructing an almost indefinite number of automatons.
 
===Environment===
[[File:H2ABridge.jpg|thumb|left|250px|An environment on [[Installation 05]].]]
Although first and foremost designed as weapons of mass destruction, the Halos are also designed as habitats for transplanted lifeforms, including but not limited to humans. After [[Master Builder]] [[Faber]]'s plans were co-opted by the [[Librarian]], the Halos were given terrestrial surfaces to support cataloged specimens. The Master Builder intended to allow these specimens to be infected by Flood forms contained on the rings, and then subsequently terminated in order to test the Halos' effectiveness.{{Ref/Reuse|c313}} The Halo installations support a wide range of environments, habitats, ecosystems, and climates. Installation 04 and Installation 05 supported warm, temperate forests<ref>'''Halo 2''', level ''[[Uprising]]''</ref> that were both deciduous and coniferous, swamps, and cold, snow covered tundra environments.<ref>'''Halo: Combat Evolved''', level ''[[Assault on the Control Room]]''</ref><ref>'''Halo 2''', level ''[[Quarantine Zone]]''</ref>  Installation 00 had climate ranging all the way from tundra,<ref name="Cov">'''Halo 3''', level ''[[The Covenant (level)|The Covenant]]''</ref> to forest,{{Ref/Reuse|Cov}} to desert.<ref>'''Halo 3''', level ''[[The Ark (level)|The Ark]]''</ref>
 
While the terrain of a Halo ring may appear to be naturally formed at first glance, it is actually artificially constructed. [[Strato-Sentinel]]s extract raw materials from the source, process them in transit, and deposit building materials at the Installation.<ref>'''[[The Art of Halo 3]]''', page 30</ref> Four huge terraforming factories then move across the face of the installation to "skin" it with landmasses and bodies of water. These factories also hold in the ring's nitrogen-oxygen atmosphere, which is then leaked out to the surface, eventually pouring through the superstructure, and tugged in place by centripetal force;<ref>'''The Art of Halo 3''', ''page 116''</ref> massive walls lining both sides of the ringworld prevent the atmosphere from leaking out into space.<ref>'''Halo: Primordium''', ''pages 40, 148''</ref>
 
An intricate layer of metallic panels is laid down several meters below the surface of the terrain, upon which rock, soil, and eventually vegetation is added. Slopes, hills and mountains can be created by sculpting these panels.{{Ref/Reuse|halo3halo}} Some features, such as landslides, are the result of time, and have been formed naturally. Others, such as the frigid conditions of the [[Quarantine Zone]] or the lake near the [[Temple (Installation 05)|Temple]] on [[Installation 05]] were artificially created.<ref>'''Halo 2''', campaign level ''[[Delta Halo]]''</ref> There are also numerous indigenous life-forms that live on the Halos; these were brought on the installations as part of the Lifeworkers' conservation project. The structures seen on the surface of the installations are built as part of the underlying structure, with the terrain then "printed" on top of them, creating the appearance of structures built into the surrounding landscape when the inverse is in fact true.{{Ref/Reuse|Lorestream}}
{{Clear}}
===Facilities===
[[File:AnniversaryControlRoom.png|thumb|250px|The [[Control Room]] of Installation 04.]]
Each Halo has several assets that are uniform to all installations. Each contains a [[control room]] located somewhere upon its inner surface. The control room houses the installation's mainframe, known as [[the Core]], from which all of the Halo's systems can be operated. The Halo's main weapon can be activated inserting the [[Activation Index]] into the Core; on the other hand, the Core may also be used to disable the main weapon.{{Ref/Reuse|Last Stand}} Each Halo also possesses a [[Library]], a large structure protected by [[Containment shield|an energy shield]] and a [[Sentinel wall|massive wall]], where the Index is housed and protected by Sentinels.{{Ref/Reuse|library}}{{Ref/Reuse|Icon}} The index itself is a semisolid [[holography|holographic]] representation of the data needed to activate the ring, and can only be directly inserted successfully by a Reclaimer.
 
Installations also possess [[Cartographer]] facilities, which contain the complete, real-time record and schematic of the installation,<ref>'''Halo: Primordium''', ''page 295''</ref> including its inner passages and networks, to be used as a navigational reference for traversing the installation. [[Flood containment facility|Flood containment]] and [[Flood research facility|research facilities]] are also standard, used by the installation's monitor to conduct research on and observe the surviving Flood specimens; these are protected by Sentinels to prevent an outbreak.<ref name="Flood240">'''Halo: The Flood''', pages 240-242</ref>
 
===Transportation===
[[File:HW2-Halo in slipspace.jpg|thumb|left|250px|Installation 09 exiting slipspace transit.]]
Facilities of the Halo Array contain advanced [[teleportation grid]]s, allowing instantaneous transportation for a Monitor or Reclaimer to any place on the installation. Under normal circumstances, these grids cannot be accessed by the Flood, though the Gravemind was able to use that of Installation 05 by controlling [[2401 Penitent Tangent]].{{Ref/Reuse|gravemind}} For Sentinels, the installation is riddled with tunnel and cave networks for access and transportation.{{Ref/Reuse|Flood240}} Teleportation grids make use of unmediated slipspace cores bound to them that generate stable, pre-computed slipspace routes between synchronised endpoints. Due to the fact that these devices have fixed endpoints (such as across an installation or its immediate vicinity), destination flexibility is sacrificed for safety, speed, and security.<ref name="WF11">''Halo: Warfleet'', p.11</ref>{{Ref/Reuse|gravemind}}
 
The Halo installations are also equipped with drive engines spaced along their rim.{{Ref/Reuse|Lorestream}} In the event of an emergency, a Halo can maneuver itself to avoid damage from a collision or weaponry.<ref>'''Halo: Cryptum,''', ''page 314''</ref> While ideally moved through fixed [[slipspace portal|portals]], the rings are able to perform slipspace jumps under their own power. In the case of at least the original twelve rings, a failsafe measure implemented in the event of capture by hostile forces would transition the Halo into slipspace and place it on a collision course with a planet or other celestial body, ensuring the weapon's destruction rather than allowing it to fall in the wrong hands.<ref>'''Halo: Primordium''', ''pages 279, 339''</ref> At the moment of [[Installation 04]]'s destruction, at least [[Alpha Shard|one major fragment]] of the ring was moved into slipspace, likely as part of a similar failsafe.<ref name="wp shard">[https://www.halowaypoint.com/en-us/universe/locations/halo-ring-fragment '''Halo Waypoint''': ''Alpha Shard'']</ref>
{{Clear}}
 
===Firing method===
[[File:H2A - Battle of Delta Halo.jpg|thumb|250px|left|Installation 05 as it aborts its firing sequence during the [[Battle of Installation 05]].]]
The seven installations in the final Halo Array function via form of lethal [[radiation]] designed to kill all [[sentience|sentient]] life in the installation's three-dimensional radius of 25,000 light-years; when fired in concert with the rest of the Array, this sterilizing effect covers the entire galaxy.<ref name="ENC">'''[[Halo Encyclopedia (2009 edition)]]''', ''pages 170-174''</ref><ref name="terminal8">'''Halo: Combat Evolved Anniversary''', ''[[Terminal (Halo: Combat Evolved Anniversary)|Terminal Eight]]''</ref>
 
When activated, the Halo rings release a burst of cross-phased supermassive neutrinos.{{Ref/Reuse|c274}} The burst possesses a harmonic frequency, which can be tuned to destroy the nervous system of any macroscopic organism that possesses one, even one as rudimentary as a notochord, as shown in the aftermath of a low-powered test firing of a Halo performed by [[Mendicant Bias]] in [[Charum Hakkor system|the system]] of Charum Hakkor. Fine tuning the pulse can also allow for selective extermination of lifeforms with varying degrees of neural complexity.<ref>[https://twitter.com/GrimBrotherOne/status/766840297498157056 '''Twitter''': ''Jeff Easterling on Twitter'']</ref> The Halo effect is able to target and eliminate most forms of neural structures, from biological nervous systems to esoteric [[neural physics]] constructs, although the effect does not extend to [[artificial intelligence]]s.<ref>'''Halo: Silentium''', ''page 310''</ref> It has been noted that neoteric array is capable of killing life with the neurological complexity above that of a bumblebee approximately.{{Ref/Reuse|Lorestream}} Simpler life forms that do not possess a neural system, such as microbes, fungi, algae, mosses, and traditional plants are unaffected.<ref name="c131">'''Halo: Cryptum''', ''pages 131-133''</ref> While organisms aboard the twelve older rings were safe from the Halo effect itself due to its directional nature, any sentient being would still experience an uncomfortable sensation in the vicinity of the pulse.<ref>'''Halo: Silentium''', ''pages 272-273''</ref> The semi-directional pulse of the senescent rings allowed for localised cleansing of star systems and clusters.{{Ref/Reuse|Lorestream}} Any living creature on the newer seven rings, however, would be killed and need to be reintroduced following the firing of the array. Furthermore, a key difference in the firing of the senescent and neoteric array is that the latter targets higher orders of life that are more complex neurologically, whereas the former will target and kill all life, which would lead to a complete collapse of planetary ecosystems as even insects are targeted. {{Ref/Reuse|Lorestream}}
 
Like virtually all Forerunner technology, the Halos are powered by [[vacuum energy]]. When the main weapon is fired, vacuum energy is siphoned from local space-time to near-depletion.{{Ref/Reuse|s270}} The pulse of the main weapon is amplified by a series of [[phase pulse generator]]s and channeled toward the Halo's center. A concentration of energy collects into the hub of the installation, which, when the weapon is fully charged, blasts outward in all directions.{{Ref/Reuse|terminal8}}
 
The radiation is propelled at superluminal speeds and will eventually propagate at a near-infinite velocity. This was known to generate causal paradoxes when the rings first fired, with two of the Halos reporting pre-echoes of the combined activation ''before'' the rings had been fired.{{Ref/Reuse|sil326}} Once activated from Installation 00, all installations will cumulatively trigger one another as their radiation fields intersect, amplifying the effects of each individual Halo.{{Ref/Reuse|s312}} The energy discharge covers the Array's effective range and cleanses it of all affected sentient life.{{Ref/Reuse|terminal8}} Individual Halos can also be fired independently from the rest of the Array; this is known as a "tactical pulse".{{Ref/Reuse|thecovenant}}
 
In the event a Halo's activation is canceled, a burst of energy is fired from the control center into the hub, causing the energy collected there to violently implode, then dissipate harmlessly.{{Ref/Reuse|great journey}}
 
The final Halo Array, comprising the six smaller Halos (and the reduced Installation 07) were designed to fire in all directions, within a spherical radius of 25,000 light-years;{{Ref/Reuse|radius}} together, the rings were capable of killing all sentient life within three radii of the Milky Way's center.{{Ref/Reuse|radius}} The original twelve Halos were designed to fire laterally, generating a cone-shaped field with a maximum effective range of hundreds of thousands light-years. When fired from the greater Ark to the [[Path Kethona|Large Magellanic Cloud]], the blast was wide enough to cover the entire 14,000 light-year-wide satellite galaxy.{{Ref/Reuse|s273}} The rings could also be fired on a lower power setting, cleansing specific planets or systems within a relatively small area of effect.{{Ref/Reuse|c131}}
 
===Effects===
[[File:Killed by Halo Effect.jpg|thumb|250px|A creature is killed by the activation of the Halo Array and is instantly decayed by the Lifeworker solvent.]]
The nervous systems of all beings are targeted by the Halos and destroyed, rendering them useless to the Flood; however, the Halo effect does not disintegrate biomass, leaving the victims' bodies mostly intact.<ref>'''Halo 3''', ''Terminal 6'' (''"I toss around [37,654 tonne] dreadnoughts like they were fighters; dimly aware of the former crews being crushed to liquescence."'')</ref> Left untreated, lifeforms killed by the pulse will decay in great masses, which could lead to ecological devastation spread by a miasma of rotten biomatter. Therefore, [[Lifeworker]]s sprayed target biospheres with a [[solute]] that would cause any animal killed by the Array to instantly decay into its component molecules,<ref>'''Halo: Silentium''', ''String Two''</ref> resulting in flash-desiccation.{{Ref/Reuse|terminal8}} Due to the Forerunners' use of solute, 21st century paleo-archeological studies gave no indication of the mass extinction caused by the Array's firing. However, in [[2332]] the [[Ross-Ziegler Blip]] revealed a tiny aberration in Earth's fossil records.<ref>'''Halo: Evolutions - Essential Tales of the Halo Universe''', ''"From the Office of Dr. William Arthur Iqbal"'', ''page 519''</ref>
 
The only known ways to avoid the effects of the pulse are to seek shelter in a [[shield world]] or to escape outside the range of the Array.{{Ref/Reuse|great journey}} However, the effects can be nullified by using a ring in an incomplete state. When [[Installation 08]] was fired in an incomplete state, [[John-117]] survived aboard the {{UNSCShip|Forward Unto Dawn}}, the Covenant Loyalists survived aboard [[Anodyne Spirit]], and native animals on Installation 00 also survived the firing. Flood aboard [[High Charity]] also survived the firing, but [[Installation 00]]'s Sentinels were able to contain those that survived with a [[containment shield]] around the ruined structure.
 
Halo Installations make use of [[Composer]] technology to an unknown degree as part of their firing.{{Ref/Reuse|Lorestream}}
 
===Protocol===
{{Main|Containment protocol}}
Each Halo ring can be activated individually by a [[Reclaimer]], also placing the other installations in standby mode, or they can all be activated simultaneously from Installation 00. In the event of a major Flood outbreak, an installation's monitor will seek out a Reclaimer if available, whom they will enlist to aid them. It will [[Slipspace translocation|teleport]] them to the installation's Library and will assist the individual in retrieving the Index. The monitor then stores the Index within its data arrays for safe transportation, lest the Reclaimer fall prey to the Flood before they can activate the installation. Once at the control room, the Reclaimer is given back the Index and must insert it into [[the Core]] in order to begin the activation sequence. At any point during the charging sequence, a Reclaimer is able to abort the firing by removing the Index from the Core.{{Ref/Reuse|great journey}}
 
===Defenses===
Each Halo ring has its own defenses, though Sentinels from Installation 00 are always deployed at a newly constructed ring to finalize preparations to launch it. [[Retriever Sentinel]]s are also stored inside the rings and will deploy automatically to attack anything deemed a threat.<ref>''Halo Wars 2'', campaign level, ''[[The Halo]]''</ref> The threat of the Sentinel defenses of Installation 03 were cause for [[Ivanoff Station]] to keep a permanent complement of [[F-41 Broadsword|Broadsword]] fighters and [[Mark 2551 Onager]] defense cannons on hand at all times, to ensure the station's defense.<ref name="ivanoff">'''[[Halo: Warfleet – An Illustrated Guide to the Spacecraft of Halo|Halo: Warfleet]]''', ''Space Stations'', ''pages 34-35''</ref> The exterior band of Halo installations contains a series of [[Confidence-class weapon array|''Confidence''-class weapon arrays]], which can be used to enforce an exclusion zone of up to one light-year. UNSC ''Pillar of Autumn'' was initially tagged as a hostile by 343 Guilty Spark using Installation 04's ''Confidence''-class defense system, but was given clearance after scans revealed that humans were aboard.<ref name="lorestream">[https://www.youtube.com/watch?v=fYaxRoAf96s '''YouTube:''' ''Halo Lore Stream: The Halo Array'']</ref><ref name="CEATerminal1">[[Halo: Combat Evolved Anniversary Terminals]]</ref>
{{clear}}
 
==List of installations==
 
===Prototypes===
{| class="wikitable" style="width:100%; border:1px solid #999999; background: #FFFFFF;"
! style="width:100px;" | Name
! style="width:100px;" | Location
! style="width:100px;" | Monitor
! style="width:100px;" | Status
|-
|[[Prototype Halo installation|Miniature Halo installation]]
|Hidden sector of the galaxy in orbit of a rogue planet
|None
|Destroyed
|}
 
===Senescent Array===
{| class="wikitable" style="width:100%; border:1px solid #999999; background: #FFFFFF;"
! style="width:100px;" | Name
! style="width:100px;" | Location
! style="width:100px;" | Monitor
! style="width:100px;" | Status
|-
|[[Greater Ark]]
|Extragalactic space
|[[Offensive Bias]]
|Destroyed
|-
|[[Gyre 01]]
|N/A
|N/A
|Destroyed
|-
|[[Gyre 02]]
|N/A
|N/A
|Destroyed
|-
|[[Gyre 03]]
|N/A
|N/A
|Destroyed
|-
|[[Gyre 04]]
|N/A
|N/A
|Destroyed
|-
|[[Gyre 05]]
|N/A
|N/A
|Destroyed
|-
|[[Gyre 06]]
|N/A
|N/A
|Destroyed
|-
|[[Gyre 07]]
|N/A
|N/A
|Destroyed
|-
|[[Gyre 08]]
|N/A
|N/A
|Destroyed
|-
|[[Gyre 09]]
|Orbiting the greater Ark
|N/A
|Destroyed
|-
|[[Gyre 10]]
|N/A
|N/A
|Destroyed
|-
|[[Installation 07|Gyre 11]]
|N/A
|[[117649 Despondent Pyre]] (formerly)
|Changed into Installation 07
|-
|[[Gyre 12]]
|N/A
|N/A
|Destroyed
|-
|}
 
===Neoteric Array===
The installations in the neoteric{{Ref/Reuse|neoteric}} Halo Array are numbered in the order they were built in,{{Ref/Reuse|neoteric}} while their alphabetical designations were assigned in the order in which they were fired, with [[Installation 04|Alpha Halo]] being the first ring to fire.<ref>''Halo: Silentium'', p. 327</ref> Although [[Installation 07]] was originally constructed as part of the first series of larger Halos, it was the last ring to be added to the neoteric Array while being heavily modified to suit its new role, hence the designation.<ref>[https://www.reddit.com/r/halo/comments/70wbxc/return_to_the_denomination_installation_04_b_c/dn76qup/ ''Reddit: Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS'' (comment by GrimBrotherOne)]</ref>
 
{| class="wikitable" style="width:100%; border:1px solid #999999; background: #FFFFFF;"
! style="width:100px;" | Designation
! style="width:100px;"  | Name
! style="width:200px;" | Location
! style="width:250px;" | Monitor
! style="width:250px;" | Status
|-
|[[Installation 00]]
|Lesser Ark
|[[Intergalactic space|Extragalactic space]]
|[[000 Tragic Solitude]] ''(destroyed)''
|Heavily damaged, then repaired; contested between the [[Banished]] and the {{UNSCShip|Spirit of Fire}}
|-
|[[Installation 01]]
|Beta Halo
|[[Auric]] orbit, [[Myung system]]{{Ref/Book|Id=enc22p345|Enc22|Page=345}}, [[Orion Arm]]<ref name="WarfleetGalaxy">''[[Halo: Warfleet]]'', p. 12-13</ref>
|[[001 Shamed Instrument]]
|Intact
|-
|[[Installation 02]]
|Epsilon Halo
|[[Taphro]] orbit, [[Zhagolin system]]{{Ref/Book|Id=enc22p347|Enc22|Page=347}}, [[Norma Arm]]{{Ref/Reuse|WarfleetGalaxy}}
|[[007 Contrite Witness]]
|Intact
|-
|[[Installation 03]]
|Gamma Halo
|[[Doavyn]] orbit, [[Khaphrae system]], [[Scutum-Centaurus Arm]]{{Ref/Reuse|WarfleetGalaxy}} {{C|formerly}}
|[[049 Abject Testament]] ''(missing)''
|Major surface damage; control room ejected and destroyed
|-
|[[Installation 04]]
|Alpha Halo
|[[Threshold]] orbit, [[Soell|Soell system]], [[Orion Arm]]{{Ref/Reuse|WarfleetGalaxy}}
|[[343 Guilty Spark]] ''(absent)''
|Destroyed; wreckage under [[Joint Occupation Zone|joint]] [[UNSC]]-[[Swords of Sanghelios]] quarantine per the [[Treaty of 2552]] preventing the return of either faction
|-
|[[Installation 05]]
|Delta Halo
|[[Substance]] orbit, [[Coelest system]], [[Norma Arm]]{{Ref/Reuse|WarfleetGalaxy}}
|[[2401 Penitent Tangent]]
|Surface [[Glassing|glassed]]; under joint UNSC-Swords of Sanghelios quarantine
|-
|[[Installation 06]]
|Kappa Halo
|[[Haakuth]] orbit, [[Mdorkon system]]{{Ref/Book|Id=enc22p349|Enc22|Page=349}}, [[Perseus Arm]]{{Ref/Reuse|WarfleetGalaxy}}
|[[16807 Abashed Eulogy]]
|Intact
|-
|[[Installation 07]]
|Zeta Halo<br>Gyre 11 {{C|Originally}}
|Unknown {{c|currently}}{{Ref/Reuse|OI09}}{{Ref/Reuse|RP13}}<br>[[Ephsu I]] orbit, [[Ephsu system]], [[Sagittarius Arm]]{{Ref/Reuse|WarfleetGalaxy}} {{c|formerly}}
|[[117649 Despondent Pyre]] ''(destroyed)''<br>[[Adjutant Resolution]]
|Damaged, controlled by the Banished
|-
|}
 
======Replacements======
{| class="wikitable" style="width:100%; border:1px solid #999999; background: #FFFFFF;"
! style="width:100px;" | Designation
! style="width:50px;"  | Original
! style="width:100px;" | Name
! style="width:200px;" | Location
! style="width:100px;" | Monitor
! style="width:100px;" | Status
|-
|[[Installation 08]]<ref name="RedditGrim">[https://www.reddit.com/r/halo/comments/70wbxc/return_to_the_denomination_installation_04_b_c/dn6n4h7/ ''Reddit: Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS''] "Sorry, 08 and 09 make way more sense :-)
In actuality, they aren't meant to directly replace an individual ring, but to replace the loss in coverage that ring offered the galaxy.",
[[Jeff Easterling]]</ref>
|Installation 04
|Alpha Halo (replacement)
|Destroyed over Installation 00
|343 Guilty Spark ''(absent)''
|Destroyed
|-
|[[Installation 09]]{{Ref/Reuse|RedditGrim}}
|Installation 04
|Alpha Halo (replacement)
|Between Installation 00 and the Soell system
|None
|Controlled by the [[Created]]
|}
 
==Non-canon and dubious canon appearances==
===Fractures: Entrenched===
{{Notice/Fracture|Entrenched}}
On November 3, 67 AP, the Covenant captured the Project: PERPETUA's factory complex and wanted to launch the SCS ''Perpetua'', in an attempt to arrive into a Halo ring and release the "Old Ones". However, the Sky Marshals, led by Commander [[Kolby]] and [[Randall Aiken|Aiken]] managed to capture and launch the ''Perpetua''. Unknown to the Sky Marshals, the Covenant warped the ''Perpetua''<nowiki>'</nowiki>s atomic reactor with a Halo ring as a pre-defined destination.
 
On December 9, 67 AP, the SCS ''Perpetua'', alongside the surviving Sky Marshals arrived into the 30,000-kilometer Halo ring, which was anchored into a green-brown planet. After thinking on Commander Kolby's sacrifice, Aiken ordered the star-zeppelin to begin its approach to the ring's surface.
 
===Silver Timeline===
{{Notice/Silver|category=no}}
[[File:HTV-S2-Halo.png|thumb|right|Halo in ''[[Halo: The Television Series Season Two]]''.|250px]]
The [[Covenant]] sought to locate Halo using the [[keystone]]s, one of which was located on [[Madrigal/Silver|Madrigal]]{{Ref/Film|Id=Contact|TV|Episode=[[Contact]]}} and the other on [[Eridanus II/Silver|Eridanus II]].{{Ref/Film|Id=Emergence|TV|Episode=[[Emergence]]}}
 
After [[Silver Team/Silver|Silver Team]] recovered the Madrigal keystone which [[Reclaimer|responded]] to [[John-117/Silver|John-117's]] touch, John learned from [[Reth/Silver|Reth]] that the Covenant were after the ring that the keystone displayed a weapon that was the end of all life as they knew it.{{Ref/Film|Id=Unbound|TV|Episode=[[Unbound]]}} [[Miranda Keyes/Silver|Miranda Keyes]] and [[Kai-125/Silver|Kai-125]], by translating a Covenant transmission, discovered that they were seeking a Sacred Ring called Halo.{{Ref/Film|Id=Homecoming|TV|Episode=[[Homecoming (TV Series)|Homecoming]]}}
 
When John used the Madrigal keystone, following Makee's advice not to fight the visions from it, he and Makee were briefly transported into a vision of them standing on the surface of a Halo ring.{{Ref/Film|Id=Solace|TV|Episode=[[Solace (TV Series)|Solace]]}}
 
In order to help Makee convince [[Var 'Gatanai]] to go rogue, [[Cortana/Silver|Cortana]] showed him John's memory of the surface of Halo. At the same time, Halsey implored John to focus on finding Halo, believing that its secrets were the key to humanity's survival.{{Ref/Film|Id=Aleria|TV|Episode=[[Aleria (TV Series)|Aleria]]}} Cortana later came up with the idea of using the stars in Halo's sky from the vision to determine its location, but it would require John and Makee touching the keystones at the same time in order to access the vision again. Cortana warned John that the Covenant were very close to finding Halo, that they were going to use it, and that they were almost there.{{Ref/Film|Id=Onyx|TV|Episode=[[Onyx (TV Series)|Onyx]]}} After communicating with John in the vision, Makee was able to use the stars to pinpoint the Halo's location which turned out to be [[Installation 04]] in the [[Soell system]].{{Ref/Film|Id=Thermopylae|TV|Episode=[[Thermopylae (TV Series)|Thermopylae]]}}
 
By tracking Makee's ship, ONI was able to find Installation 04's location. The ring gave off a powerful energy signature that distorted their star map. When John arrived at Halo, he found the [[First Fleet of Solemn Accord]] chasing Makee towards the ring while the [[SPARTAN-III program/Silver|SPARTAN-IIIs]] under [[Kai-125/Silver|Kai]]'s command prepared to undertake a possible suicide mission that would destroy both the Covenant and UNSC fleets along with the star system and the Halo.{{Ref/Reuse|Thermopylae}}


In the course of [[Halo: Combat Evolved]], neither Threshold nor Basis is reachable, all action takes place on, in, or near the Halo installation. In [[Halo 2]] there is a [[multiplayer]] and a [[campaign]] level on a gas mining facility in Threshold's atmosphere.
==Trivia==
{{Linkbox|gallery=yes|gallerypage=Images of Halos}}
*The Halos are remarkably similar to the eponymous megastructure of [[Wikipedia:Larry Niven|Larry Niven]]'s ''[[Wikipedia:Ringworld|Ringworld]]'' series. However, Niven's Ringworld encircles a large star, whereas the Halos merely orbit planets, being much smaller than the former. The Halos are also very similar to the [[Wikipedia:Orbital (The Culture)|Orbitals]] from [[Wikipedia:Iain M. Banks|Iain M. Banks']] ''Culture'' series, though considerably smaller.
*In a ''Halo: Combat Evolved'' [[Pre-Xbox Halo|prototype]], Installation 04 had a section that was only partially constructed. This feature was dropped from the final game, though it inspired the design of Installation 08.
*The Prophet of Mercy once referred to the Halo Array's pulse as a divine wind.{{Ref/Reuse|Icon}} This is a literal translation of ''[[Wikipedia:Kamikaze|kamikaze]]'', suicide attacks carried out by Japanese pilots against Allied vessels near the end of World War II. ''Kamikaze'' aviators were willing to give their lives based on their fanatical devotion to defend [[Wikipedia:Hirohito|Emperor Hirohito]] and the state. This is mirrored by the Covenant's quest to activate the Halos and commit holy war in deference to their gods.


While the locations of the other Halo rings are unknown, it has been speculated that [[Installation 04|Alpha Halo]] was located in the [[Soell|Iota Horologii]] System.
==Gallery==
===Concept art===
<gallery>
File:H2A Terminals Concept HaloSurface.jpg|Concept art of a Halo's surface for ''[[Halo 2: Anniversary]]''{{'}}s [[Terminal (Halo 2: Anniversary)|terminals]].
File:HINF DoisacHalo Concept.jpg|Concept art of a Halo ring firing upon and destroying [[Doisac]] for ''[[Halo Infinite]]''.
File:HTV JohnHalo Concept 1.png|Concept artwork of a Halo ring dream sequence for ''[[Halo: The Television Series]]''.
File:HTV JohnHalo Concept 2.png|Concept artwork of a Halo ring dream sequence for ''Halo: The Television Series''.
File:HTV JohnHalo Concept 3.png|Concept artwork of a Halo ring dream sequence for ''Halo: The Television Series''.
File:HTV JohnHalo Concept 4.png|Concept artwork of a Halo ring dream sequence for ''Halo: The Television Series''.
File:HTV S2 Halo Structures Concept 1.jpg|Concept artwork of a Halo for ''[[Halo: The Television Series Season Two]]''.
File:HTV S2 Halo Structures Concept 2.jpg|Concept artwork of a Halo for ''Halo: The Television Series Season Two''.
</gallery>


== Trivia ==
===Illustrations===
<gallery>
File:HaloLegends-Origins-HaloArray.png|A Halo installation in ''[[Origins]]'' from ''[[Halo Legends]]''.
File:Halo-Legends-Origins-1 HaloArrayFiring.jpg|A Halo being fired in ''Origins'' from ''Halo Legends''.
File:HaloLegends-Origins-HaloPostFiring.png|A Halo ring's pulse dimming after its activation in ''Origins'' from ''[[Halo Legends]]''.
File:TML - broken Halo.png|Broken Installation 04 in ''[[The Mona Lisa]]''.
File:HE Installation 03.jpg|Installation 03 ejecting a section of itself in ''[[Halo: Escalation]]''.
File:HM-Thanolekgolo.png|Alpha Shard in ''[[Halo Mythos]]''.
</gallery>
===Screenshots===
<gallery>
File:HCE-AlphaHalo-SurfaceDetail.jpg|Installation 04 in ''[[Halo: Combat Evolved]]''.
File:Delta Halo.jpg|Installation 05 in ''[[Halo 2]]''.
File:H2_halo_surfaceland.jpg|The surface of a Halo ring.
File:Halo 3 - Installation04B.jpg|Installation 08 in ''[[Halo 3]]''.
File:LFA-43 Halo.png|Installation 04 in ''[[Halo: Combat Evolved Anniversary]]''.
File:FUD-HaloRing.jpg|A visual reference to a Halo ring in ''[[Halo 4: Forward Unto Dawn]]''.
File:H4-GammaHaloInst03-ScanScreen.jpg|Installation 03 in ''[[Halo 4]]''.
File:H2A - ZenithRing.jpg|Installation 05 in ''Halo 2: Anniversary''.
File:Halo ring and thing.jpg|A post-war human [[space station|station]] near an unknown Halo installation in ''[[A Hero Falls]]''.
File:HSS-Gamma Halo Pelican.png|Installation 03 in ''[[Halo: Spartan Strike]]''.
File:HNF-Alpha Shard.jpg|Alpha Shard in ''[[Halo: Nightfall]]''.
File:H5G-LegendaryHalo.png|Installation 07 in ''[[Halo 5: Guardians]]''.
File:HW2-Halo.png|Captain [[James Cutter]] stands before Installation 09 in ''[[Halo Wars 2]]''.
File:MCC_Halo_Background.jpg|A Halo ring in the menu background of ''[[Halo: The Master Chief Collection]]''.
File:FH4 - Halo Showcase Skybox.png|''[[The Halo Experience Showcase]]''{{'}}s unique skybox featuring a Halo ring in ''Forza Horizon 4''.
File:HI E319 TheRingReveal.png|John-117 gazing at a destroyed Installation 07 from the ''[[Halo Infinite]] [[Discover Hope]]'' trailer.
File:HINF FullZetaHalo.png|Installation 07 as viewed by John-117 in space.
</gallery>


*On the [[Halo PC]] menu, look closely at the Halo before it starts moving. Somewhere on it you can see the letters "[[Gunnery Sergeant]] Marcus", a direct reference to [[Marcus R. Lehto]].
==List of appearances==
*The Halo textures for both [[Halo: Combat Evolved]] and [[Halo 2]] are the same, and are both symmetrical. Thus, when you look straight up, a shape in the clouds of the Halo resembles a "Grey" alien. It could have been put in there on purpose, although it might be a coincidence.
{{Col-begin}}
*[[Halo: Ghosts of Onyx]] describes the Halos as being the "Sword" of the [[Forerunner]], and the [[Shield Worlds]] was their "Shield." This description is mysteriously similar to the lines [[Cortana]] says on the [[Halo 3 Announcement Trailer]]; "I am your shield, I am your sword."
{{Col-2}}
*In the clouds of Halo, on every level, you can see the face of Chris Carney. This can also be seen in [[Halo 2]].
*''[[Halo: The Fall of Reach]]'' {{1st}}
*Considering its 10,000 km diameter, Halo would need to rotate at [[7]] km/s in order to produce Earth-like "gravity". However, in the novel "The Fall of Reach", Cortana says that "some numbers don't check out" and discovers an artificial gravity field on the ring. This is another possible [[7]] reference.
*''[[Halo: Combat Evolved]]''
*In a [[Halo: Combat Evolved]] Prototype, [[Installation 04]] had a disconnected section where there is a railroad bridge that floats in space.
*''[[Halo: The Flood]]''
*As seen in the preview for the [[Smuggler (Level)|Smuggler]] Map, the names of the other five Installations are Beta, Gamma, Kappa, Epsilon, and Zeta. However, there is no consistent pattern with the names of the Installations in correlation with their numbers, so it is unknown which Installation the names apply to.
*''[[Halo: First Strike]]''
*''[[Halo 2]]''
*''[[Halo Graphic Novel]]''
**''[[The Last Voyage of the Infinite Succor]]''
*''[[Halo: Ghosts of Onyx]]''
*''[[Halo: Uprising]]'' {{Mo}}
*''[[Halo 3]]''
**''[[Bestiarum]]'' {{Mo}}
*''[[Halo: Contact Harvest]]'' {{Mo}}
*''[[Halo: The Cole Protocol]]'' {{Mo}}
*''[[Halo Wars]]'' {{Mo}}
*''[[Halo Legends]]''
**''[[Origins]]''
**''[[Homecoming]]''
**''[[Odd One Out]]'' {{C|Non-canonical appearance}}
*''[[Halo: Evolutions]]''
**''[[The Mona Lisa]]''
*''[[Halo: Reach]]''
*''[[Halo: Cryptum]]''
*''[[Halo: Glasslands]]'' {{Mo}}
*''[[Halo: Combat Evolved Anniversary]]''
**''[[Terminal (Halo: Combat Evolved Anniversary)|Terminals]]''
*''[[Halo: Primordium]]''
*''[[Halo: The Thursday War]]'' {{Mo}}
*''[[Halo 4: Forward Unto Dawn]]'' {{C|Visual allusion}}
*''[[Halo 4]]''
**''[[Terminal (Halo 4)|Terminals]]''
*''[[Halo: Silentium]]''
*''[[Halo: Escalation]]''
*''[[Halo: Broken Circle]]'' {{C|Holographic representation only}}
*''[[Halo: Nightfall]]''
*''[[Halo 2: Anniversary]]''
**''[[Terminal (Halo 2: Anniversary)|Terminals]]''
{{Col-2}}
*''[[Halo: New Blood]]'' {{Mo}}
*''[[Halo: Hunters in the Dark]]''
*''[[Halo: Last Light]]'' {{Mo}}
*''[[A Hero Falls]]''
*''[[Halo 5: Guardians]]''
*''[[Halo: Shadow of Intent]]'' {{Mo}}
*''[[Halo Mythos: A Guide to the Story of Halo]]''
*''[[Halo: Fractures]]''
**''[[Promises to Keep]]'' {{Mo}}
**''[[Untitled story (Halo: Fractures)|Untitled story]]'' {{Mo}}
*''[[Halo Wars 2]]''
*''[[Halo: Envoy]]'' {{Mo}}
*''[[Halo: Retribution]]'' {{Mo}}
*''[[Halo: Legacy of Onyx]]'' {{Mo}}
*''[[Halo: Official Spartan Field Manual]]''
*''[[Halo: Renegades]]'' {{Mo}}
*''[[Halo: Outpost Discovery]]''
*''[[Halo: Shadows of Reach]]'' {{Mo}}
**''[[Sacrifice]]'' {{Mo}}
*''[[Halo: Point of Light]]''
*''[[Halo: Divine Wind]]'' {{Mo}}
*''[[Halo Infinite]]''
*''[[Halo: The Television Series Season One]]''
**''[[Unbound]]'' {{Mo}}
**''[[Homecoming (TV Series)|Homecoming]]'' {{Mo}}
**''[[Solace (TV Series)|Solace]]''
**''[[Allegiance]]''
**''[[Transcendence]]''
*''[[Halo: The Rubicon Protocol]]''
*''[[Halo: Outcasts]]'' {{Mo}}
*''[[Halo: Battle for the Blood-Moon]]'' {{Mo}}
*''[[Halo: The Television Series Season Two]]''
**''[[Visegrád (TV Series)|Visegrád]]'' {{Mo}}
**''[[Aleria (TV Series)|Aleria]]''
**''[[Onyx (TV Series)|Onyx]]''
**''[[Thermopylae (TV Series)|Thermopylae]]''
**''[[Halo (TV Series)|Halo]]''
*''[[Halo: Epitaph]]''
{{Col-end}}


== Sources ==
==Notes==
<small><references/></small>
{{Ref/Notes}}


==Sources==
{{Ref/Sources|3}}


{{Forerunner2}}
==See also==
*[[The Anatomy of Halo]]
*[https://www.youtube.com/watch?v=fYaxRoAf96s Halo Lore Stream: The Halo Array] - a lore stream conducted by [[Jeff Easterling]] and [[Kenneth Peters]], focusing on the Halo Array.
{{Forerunner|array}}


[[Category:Halos]]
[[Category:Halo Array| ]]
[[Category:Astronomy]]
[[Category:Forerunner weapons]]

Latest revision as of 04:30, November 13, 2024

"Halo" redirects here. For other uses, see Halo (disambiguation).
The Array at Installation 00, just before their departure to firing sites across the galaxy.

"Halo doesn't kill Flood, it kills their food! Humans, Covenant, whatever—we're all equally edible! The only way to stop the Flood is to starve them to death. And that's exactly what Halo is designed to do: wipe the galaxy clean of all sentient life!"
— Cortana during the Battle of Installation 04.[1]

The Halo Array, sometimes known simply as Halo[2] or the Array,[3][4] is a network of colossal ring-shaped superweapons individually known as Halos or Halo rings, constructed by the Forerunners.[5] The Halos were also referred to by the Covenant as the Sacred Rings,[6][7] and labeled as Installations or infrequently referred to as Fortress Worlds[8] by the Forerunners and their monitors.

The first array of twelve Halos was constructed by order of Master Builder Faber circa 98,445 BCE with the intent of being an ultimate weapon, one that would secure the preeminence of the Builder rate in Forerunner society.[9] Later, the weapons would be refined further and a new array of six smaller and significantly more lethal installations was constructed; the newer Halos are known as the "neoteric" rings.[10] Eventually, eleven were destroyed and/or lost while the remaining seven were used by the Forerunners as a last resort when combating the parasitic Flood.[11] All sentient beings in the galaxy were killed, robbing the Flood of hosts and starving it to death.

In addition to serving as weapons of last resort, Halo installations are also research facilities dedicated to containing and studying many different kinds of life forms. The life forms that were hand-selected by the Librarian included marine life, fauna, and land vertebrates. With the Master Builder's permission, the Librarian would research each animal to detect if their bodies reacted to Flood infection. The research on the animals would be more deeply analyzed if they did become infected. The Librarian's studies also helped determine if the rings could be used to repopulate the galaxy as part of the Conservation Measure.[11][12]

Background[edit]

A section of a Halo's surface.

"After exhausting every other strategic option, my creators activated the rings. They, and all additional sentient life in three radii of the galactic center, died, as planned."
— 343 Guilty Spark during the Battle of Installation 05.[13]

As it is known in modern times, the Halo Array is a network of seven ring-shaped megastructures created by the Forerunners, designed to exterminate all sentient life within the Milky Way galaxy.[13] Built following the Human-Forerunner War, these ringworlds were later used as a last resort against the Flood, a parasitic extra-galactic species that threatened to consume every sentient life-form in the galaxy. By activating the rings, the Forerunners wiped out every sentient being in the galaxy, effectively starving the Flood to virtual extinction, though specimens were kept in a number of Forerunner containment facilities, including the Halo installations themselves.[14]

A total of eighteen Halo rings existed during the reign of the Forerunners; an older array of twelve 30,000-kilometer-wide rings produced by the greater Ark and six 10,000-kilometer rings, constructed at the newer lesser Ark. Of these, only seven survived to be included in the final Array. The Halos were originally deployed in orbit over large gas giants.[15] However, as of 2557, Installation 03 orbited a rocky planet.[16] Installation 04 maintained an atmospheric mining facility in its anchor planet Threshold's atmosphere until it was destroyed by the Covenant.[17]

Though separated by thousands of light-years, the installations are networked together and capable of remote activation at the Ark, their extragalactic construction foundry. Each Halo installation has a maximum effective range of 25,000 light-years in every direction.[18][19] The method utilized by the array to conduct this "mass sterilization protocol"[20] involves the superluminal conveyance of a burst of cross-phased super-massive neutrinos, tuned to emit a harmonic frequency that destroys the nervous system of any life form within range. Simpler organisms lacking a neural system are unaffected, along with inanimate structures. Precursor technology, however, is extremely susceptible to damage from the Halo effect due to its quasi-living neural physics composition.[9][21]

Readout of the seven Halos.

The Halo Array in its entirety has been fired only once in known history, approximately 100,000 years ago, by the IsoDidact in order to stop the Flood from overwhelming the galaxy. All beings in the Array's effective range, including Forerunners themselves, were wiped out by the Array's pulse,[13] with the exception of those who took refuge on the shield worlds. A number of Forerunners survived at the lesser Ark but chose to exile themselves from the galaxy.[22] The array has come close to activation four times since; Installation 04 was almost activated by the Master Chief, Installation 05 was activated by Commander Miranda Keyes at the behest of the Jiralhanae Chieftain Tartarus, Sergeant Johnson was forced by the Prophet of Truth to activate the Array from the Ark, and Bobby Kodiak was forced by 000 Tragic Solitude, the Monitor of the Ark, to activate the Halo Array from the Ark as a revenge. None of these attempts were successful; the first was stopped by Cortana, while the other three attempts were halted by UNSC and Sangheili intervention. A replacement Halo for the destroyed Installation 04 was activated outside of the galaxy, meant to eliminate the Flood massed at Installation 00. Upon firing, its incomplete state caused the ring to shake itself to pieces, with the resulting explosion damaging the Ark. However, some Flood forms survived the activation.[23]

Each of the Halo installations manufactured at Installation 00 is given a sequential designation number based on their order of construction, beginning from 01,[10] and is overseen by a single monitor. The monitors are given control of the Installations' Sentinel automatons, from Aggressors to Constructors and Enforcers, and are responsible for containing the Flood test subjects in their research facilities and protecting the Halo from intruders.

The Array also encompasses Installation 00, an extra-galactic construction facility that can create replacement installations in the event that one is destroyed. All Halos can also be remotely activated from the Ark without being subjected to their effects, as the megastructure is out of the Array's range.[24] The Forerunners also built shield worlds as a means to escape the effect without having to leave the galaxy.[25]

History[edit]

Construction[edit]

A Forerunner observes the construction of a Halo.

The first Halos were constructed by the Master Builder Faber and his Builders in the millennia after the Flood was first encountered in the Milky Way, only to eventually retreat, seemingly due to early humanity's efforts. The most extreme faction of Builders, which at the time controlled the Ecumene Council, claimed that more extreme measures should be used to protect the galaxy against a possible Flood resurgence and proposed building the Array for this purpose. The initial iterations of the weapon system that would eventually become Halo did not share the circular shape of the final installations.[26] Although they faced strong opposition from the Prometheans, led by the Didact, for thousands of years, the faction eventually won the approval of the Council and commenced work on the Array.[9] Several prototypes of the Halos were constructed and powered by their host facilities, with one such installation orbiting a rogue planet.[27]

However, at this point, the Librarian went to the Council and invoked the Mantle, stating that the Halos should be used as biological preserves in the Conservation Measure, a plan to repopulate the galaxy should the Array ever be activated. The Council approved her request, and ordered that the Halo installations be constructed to have a range of natural environments for the Lifeworkers to preserve their biological specimens in. The Builders also agreed, seeing the inclusion of biological preserves as an effective means of competing with the Didact's shield worlds which incorporated similar measures.[28] However, the Master Builder later altered the initial plan, and his researchers began to use these specimens for a series of brutal experiments involving Flood infection.[29]

Twelve Halos, each 30,000 kilometers in diameter, were originally commissioned by Master Builder Faber and constructed by Wise-Hands-to-Forge's guild at the greater Ark, the first Ark installation to be constructed. Only one of these original rings ultimately survived to be used in the Forerunners' final plan; this ring was designated Installation 07. Later on, an improved, separate array of six installations was constructed at the lesser Ark,[30][31] although the construction of the second Ark and its more powerful Halos was delayed by the Council for some time to prevent the Builders from becoming too powerful.[32]

In the later stages of the construction of the first Halos, a Builder named Maker-of-Moons was assigned to improve upon their designs. The first test deployments had proven the original rings to be unstable and too large to be practically deployed, generating enormous particle reconciliation debt when moved. The original Ark also had several flaws, including the inability to construct smaller installations. Although initially reluctant to admit these defects,[33] the Master Builder, informed by Maker's analysis, commissioned a new Ark and a series of new, more efficient rings several millennia after the first Halos were made; the Builders promoted this as a means to save even more species while being able to create more Halos. The new Ark, known as the lesser Ark or Installation 00, and its six new Halos were constructed in secret,[28] their location known only to the Master Builder.[34]

The final Array, activated at the conclusion of the Forerunners' conflict with the Flood, comprised seven rings, each 10,000 kilometers in diameter, one of them being the reduced Installation 07.[35]

Forerunner-Flood war[edit]

An illustration of Maethrillian, the Halo Array, and a number of Aggressor Sentinels.
The original Halos gathered in orbit around Maethrillian.

The first test of a Halo installation was conducted by Mendicant Bias, who fired Installation 07 in the system of Charum Hakkor and Faun Hakkor on a low power setting, destroying all of the sentient life on the latter planet and inadvertently releasing the Primordial, an extant Precursor entity, from captivity on the former planet. Mendicant Bias then brought the released being to the Halo for study and began a 43-year-long interrogation of it. Eventually, Mendicant Bias disappeared with Installation 07 after being corrupted by the Primordial.

Following the use of a second Halo by Master Builder Faber to suppress a rebellion on the San'Shyuum homeworld of Janjur Qom, the other eleven Halo installations were taken to the Forerunner Capital during the tribunal against Faber, where it was to be decided whether to decommission them. However, in the midst of the trial, Mendicant Bias, turned rampant by the Primordial, appeared with Installation 07, which had gone missing following the ancilla's corruption and assaulted the Capital. The AI attempted to seize control of the remaining Halos and fire them, but was only able to control five out of the twelve. One of those five was destroyed by the combined tidal forces of the Capital, the firepower of local Forerunner fleets, and the stress of a recent slipspace transition. The seven Halos that Mendicant Bias was unable to control were recalled to Installation 00 via a slipspace portal, yet only one escaped before the portal collapsed, with the other six breaking up in slipspace.

Installation 07 jumped into a distant system on a pre-designated destructive collision course with a planet—a security measure put in place in the event that it fell out of Forerunner control. The installation was eventually reclaimed by the IsoDidact's forces, and it survived the passage of the planet despite taking heavy damage. A significant amount of the ring's superstructure was discarded, reducing its size to 10,000 kilometers, in order to allow it to perform a successful slipspace jump to the greater Ark. The installation's surviving biological specimens were transported on the Ark and the Flood outbreak on the ring was contained. The ring was refitted to enable it to function in concert with the six final Halos and deployed to its final station in the galaxy; the distribution of the final Halo Array would follow several years later.[35]

During the battle at the Capital and the years that followed, all but one of the original twelve rings—Omega Halo—apart from the repurposed Installation 07 were hunted down and destroyed by the Flood.[36] In the final hours of the Forerunner-Flood war, the ecumene's leadership retreated to the greater Ark, also home to Omega Halo. When a Flood attack became imminent, it was decided that the IsoDidact go to the lesser Ark where he would deploy and fire the final Halo Array. Before relinquishing the coordinates to his secret Ark,[34] the Master Builder met the IsoDidact in the control room of Omega Halo and fired the ring, obliterating a small portion of the star roads laying siege on the Ark and cleansing the Large Magellanic Cloud of life.[37]

Activation[edit]

Main article: Great Purification
Installation 00 sending the Halo Array through a slipspace portal during the Forerunner-Flood war.

The Flood and the star roads destroyed both Omega Halo and the greater Ark, but the IsoDidact managed to escape to Installation 00 to fulfill his mission. Arriving at the lesser Ark, the IsoDidact had the rings' Index collection distributed to their respective installations aboard a Lifeworker vessel over the Ark. The installations' primary monitors were also formally given their assignments to their final posts. Each monitor received a new name and numeric designation, each intended to serve as a form of memorial to the Forerunners.[38] With the assistance of Offensive Bias, the IsoDidact deployed the remaining six Halos from the Ark's Citadel. Together with Installation 07, these installations comprised the final Halo Array of seven rings.[35]

The Halo Array fires, ending the conflict.

As Mendicant Bias and the Flood prepared their final assault on the lesser Ark in order to stop the firing of the Halos, the IsoDidact activated the Array. Installation 04 was first in the Array to fire, with the others following sequentially as their fields intersected.[39] The pulse covered the entire galaxy, killing all sentient life within range and destroying the Precursors' neural physics architecture, including the Domain the Forerunners used to hold dear.[40] Whether the pulse would destroy star roads and other Precursor artifacts in faster-than-light transit was uncertain even to the Forerunners themselves, due to the largely unknown mechanisms of Precursor superluminal travel.[41] However, their total destruction seems apparent from the fact they were no longer in evidence when the Forerunners repopulated the galaxy.[22]

It was later discovered that a species called the Xalanyn had somehow survived the firing of the Halo Array. Frightened that the Xalanyn would eventually become the dominant species of the galaxy and claim the Mantle of Responsibility, the Forerunners brought Installation 07 into orbit of the Xalanyn homeworld under the pretense of a meeting and imprisoned them on the ring for containment and study.[42]

Post-activation[edit]

The seven Halos then remained relatively dormant for approximately 100,000 years, though at least Installation 05 experienced a major Flood outbreak, while Installation 04 was visited briefly by other species,[43] including a major crash-landing in 40,000 BCE.[44]

The Array's activation caused catastrophic damage to ecosystems across the galaxy, with innumerable species both sentient and non-sentient rendered extinct. The dissolving of dead bodies thanks to solute eventually showed up on the fossil record, and was labeled by scientists as the Ross-Ziegler Blip. This curious gap was dismissed as an anomaly caused by spatial distortion until humanity discovered the Array in 2552. Several species indexed by the Library Project did not survive reintroduction to their homeworlds, and those that did were all reverted to a Tier 7 technological state. The mostly uneventful period starting after the firing of the Halos was known as the dark time.

The Covenant, a theocratic multispecies alliance, was founded on the misguided belief that the Halo Array was actually the source of a "Divine Wind" that allowed the Forerunners to transcend the physical. By activating the Array, they too could embark on this "Great Journey" and join the Forerunners in godhood.

Rediscovery[edit]

The destruction of Installation 04.

Eventually, the stellar coordinates of Installation 04 were discovered through the combination of a crystal artifact on Sigma Octanus IV and a huge Forerunner artifact buried under the surface of Reach. The coordinates were utilized by the UNSC Pillar of Autumn's shipboard AI Cortana to escape from the Fall of Reach. The cruiser arrived over the Installation's orbit and was subsequently shot down by Covenant ships. Most of the ship's combat personnel escaped and made landfall on the artificial construct, triggering the Battle of Installation 04.

During their investigations on Installation 04, the Covenant encountered a Flood containment facility and unknowingly released the dormant Flood; they quickly, but only partially, reestablished containment. Soon, a squad of Marines led by Captain Jacob Keyes accidentally broke quarantine again, expecting to find a large Covenant weapons cache. The human-waged guerrilla war quickly turned into a massive four-way battle between UNSC forces, the Covenant, Sentinels led by 343 Guilty Spark, and the Flood.

The partially constructed Installation 08 hovering over the Ark.

The battle finally culminated when Spartan John-117 detonated the fusion engines of the Pillar of Autumn on the surface of the installation, which compromised the structural integrity of the ring. The gravitational momentum and inertia still perpetuating the ring in orbit around Threshold then tore the ring apart. The remains of Installation 04 were scattered as debris in space. The explosion sent massive chunks of the ring careening into Basis; the moon suffered a constant bombardment of debris from the ring after its destruction.[45]

After escaping the Battle of Tribute, a UNSC freighter, Floral Express, discovered Installation 03 on October 8, 2552. By October 25 neutralization protocols had been established.[46]

Later, the Covenant discovered a third Halo, Installation 05. On this Halo, the Flood had already been released and much of the ring had been compromised, including its monitor, 2401 Penitent Tangent. Soon, another four-way conflict began. The battle ended in the Flood manifesting a Gravemind and successfully escaping the ring aboard the infected UNSC In Amber Clad. The ring was nearly activated by Tartarus, the Chieftain of the Jiralhanae, but Commander Miranda Keyes pulled the Activation Index out of the installation's core at the last moment, causing all six functional installations to go into "standby mode", ready for remote activation from the Ark.

The human survivors returned to Earth and resumed their fight against the Covenant, who had uncovered a large structure on Earth, which they assumed to be the Ark. The Covenant landed the keyship Anodyne Spirit in the center of the structure, activating it. However, the structure was soon revealed not to be the Ark, but a generator of a portal to the actual Ark, a massive artificial world located outside the galaxy. Human and Sangheili forces proceeded through the portal to the newly-discovered installation to prevent the Covenant from activating the remaining Halo rings remotely. Eventually, the Gravemind arrived at the Ark aboard High Charity, the Covenant's capital city, which had been turned into a Flood hive. The hive crashed onto the installation, releasing the Flood.

Soon, 343 Guilty Spark, John-117, and Arbiter Thel 'Vadam discovered that the Ark had been constructing a new Installation 04, to replace the one which had previously been destroyed. This new installation was only days from being completed. The humans decided to activate the new ring to stop the Flood, resulting in the incomplete ring destroying itself,[47] severely damaging the Ark in the process.[48]

Post-Covenant War[edit]

The UNSC Infinity approaches Installation 03, as confirmed on page 349 of the Halo Encyclopedia (2022 edition).
The UNSC Infinity approaches Installation 03.

By January 2553, the UNSC had begun an active search for the remaining Halo installations, with the intent to decommission them.[49] By at least July 2557, UNSC scientists were studying the Array for decommissioning, with facilities at Installations 03 and 05. Installation 00 was scouted by both automated probes and the ONI vessel UNSC Rubicon, which was lost several days after its arrival due to the actions of 343 Guilty Spark.[50]

Installation 07 was discovered in early 2555 due to records found on Sarcophagus by Dr. Luther Mann with an ONI research group stationed on the ring immediately afterward. A crisis occurred when it was discovered that Installation 07 — as well as the other Halos — were counting down to activation in five weeks from March 8, 2555. As the stand-by failsafe protocol had never been deactivated, it was realized that the Ark was the only location where the Array could've been activated. With the help of Huragok Drifts Randomly, the Portal at Voi was reactivated, but Earth came under attack from Retriever Sentinels from the Ark. A joint UNSC-Swords of Sanghelios mission was launched to the Ark where it was discovered that the Ark's now-rampant monitor, 000 Tragic Solitude, had initiated the activation with the help of Bobby Kodiak. Having witnessed the destruction sentient life caused, particularly to Forerunner constructs, Tragic Solitude had activated the Array for a two-fold reason: to trick humanity into reactivating the portal so he could strip-mine Earth for materials to repair the Ark and eliminate the sentient species of the galaxy. Mann was able to deactivate the Array from the Ark and the team forced Tragic Solitude to end the Invasion of Earth. After Tragic Solitude attacked again, he was destroyed by Bobby Kodiak at the cost of his own life, ending the threat the rogue monitor posed to sentient life.[51] At some point following the loss of Installation 08, Installation 00 began to construct a new replacement, one that would be maintained in the Ark's Foundry in a near-finished state for some time.[52]

In February 2556, the Outer Colony world of Sedra suffered a deadly bioweapon attack by a Sangheili terrorist. The bioweapon source was traced to a new element mined from a surviving fragment of Installation 04, created by the supernova-level explosion that had destroyed the original installation. A joint ONI-Sedran Colonial Guard mission was launched to capture the human smugglers mining the element and to destroy the deposits to prevent future use of the bioweapon. Though most of the team was killed, ONI Lieutenant Commander Jameson Locke and Sedran Private Talitha Macer escaped in the smugglers' Bactrian-class freighter while Colonel Randall Aiken sacrificed himself to destroy the deposits and the fragment's resident Lekgolo population with a HAVOK tactical nuclear weapon.[53]

By early 2557, humanity had returned to the Ark and set up the Henry Lamb Research Outpost. Under the guidance of the smart AI Isabel, the researchers began directing Retriever Sentinels to strip-mine lifeless systems to repair the Ark. The reconstruction slowly reached full automation until the humans were no longer needed to nudge it along. Over time, the Ark was repaired with noticeable differences between one day and the next over only the course of three months.[54]

Later, the scientists studying Installation 03 located the Composer on the ring and accidentally activated it, causing them to become digitized. However, the sensor data left over from the incident led to the discovery of the shield world Requiem. Later, the Didact traveled to Ivanoff Station near Installation 03 to retrieve the Composer and used the device to harvest the essences of the entire research staff before heading for Earth.[55] Meanwhile, Jul 'Mdama's Covenant and their Promethean allies attempted to take control of Installation 03 by using the Conduit to open slipspace portals across the ring, but the attack was repelled by a Spartan Headhunter.[56]

The second replacement Halo above the Ark in 2559.

A day later, after the Didact's defeat at Earth, the Forerunner and some of his Promethean forces fell on Installation 03 via a slipspace portal. SPARTAN-II Blue Team followed, resulting in a skirmish fought on both Installation 03 and the Composer's Forge. The Forge's monitor, 859 Static Carillon, transported Installation 03 over the Forge for the Didact, who intended to use the ring to finally destroy humanity.[57] However, the monitor instead allied with the Spartans due to his disagreements with the Didact and helped them defeat the Forerunner. After John-117 disabled the Halo's failsafes, Static Carillon ejected the segment housing the control room, causing it to fall upon the Composer's Forge. The monitor then stabilized the ring and took it to an unknown location for repairs.[58]

In late 2558, Installation 00 became a battlefield once again as the mercenary organization known as the Banished arrived there following a sudden shutdown of the Earth portal. The Banished launched an assault on the UNSC bases on the Ark and soon gained control of the entire installation. In May 2559, the UNSC Spirit of Fire, having drifted in space for 28 years, was mysteriously transported to Installation 00 by an agency evidently within the Ark.[59] During the ensuing conflict between the UNSC and the occupying Banished forces, Professor Ellen Anders learned of the contingency ring held within the Foundry and was able to launch the new Halo, with the intent of deploying it to Installation 04's former site in the Soell system where a distress beacon could be raised to the UNSC.[52] While the Halo was successfully sent through the portal, its firing mechanism disabled by Professor Anders, the ring was intercepted and forced out of slipspace on the way by a Guardian.[60]

In October 2559, the Banished succeeded in opening a slipspace portal to Reach through which Atriox and some of his forces returned to the Milky Way galaxy in a Eklon'Dal Workshop Lich. Before the portal was shut down, Castor and his small detachment of the Keepers of the One Freedom hijacked Atriox's Lich and used it to fly back through the portal to the Ark, intending on using the Ark to fire the Halo Array and start the Great Journey.[61][62] On the Ark, the Keepers allied themselves with Prelate Dhas Bhasvod and his Dhas Bhasvod's Covenant, guided by the Forerunner archeon-class ancilla Intrepid Eye who sought to fire the Halo Array in order to destroy the Domain and defeat Cortana for the sake of her own plans. The combined factions were opposed by both forces from the Spirit of Fire and the Banished spearheaded by the Clan of the Long Shields as neither the Banished nor the UNSC wanted Castor and Bhasvod to succeed. The Covenant and Keeper forces were able to reach Epsilon Clarion, the only facility on the Ark capable of firing the Halo Array that was not inaccessible or inoperable. However, they suffered heavy casualties from UNSC and Banished attacks along the way and Castor abandoned his plans after learning the truth about the true purpose of Halo. On the order of Veta Lopis, the Spirit of Fire launched an orbital bombardment of EMP MAC rounds that destroyed Epsilon Clarion and with it, Intrepid Eye and the Ark's ability to fire the Array. The Keeper detachment was left decimated with only Castor and Sangheili Blademaster Inslaan 'Gadogai surviving while Bhasvod, after killing Mark-G313, departed to link up with the rest of his own forces.[63]

In December 2559, the Banished took over Installation 07 in search of the Xalanyn who had been imprisoned on the ring following the Great Purification. When the UNSC came to the ring in order to stop Cortana once and for all, a conflict erupted on the ring between the two sides, leading to the apparent destruction of the Infinity. In May 2560, the Harbinger succeeded in locating her species just before the Master Chief killed her. Subsequently, Atriox reached and unlocked a facility on Zeta Halo holding the cylixes of the Xalanyn. During the destruction event that shattered a portion of the ring at the hands of Cortana, Installation 07 itself was moved from the Ephsu system to an unknown location[64][65] by Cortana.[66] Lieutenant TJ Murphy speculated that it could've been moved clear across the galaxy or even into intergalactic space.[67][68]

Features[edit]

The scale of the UNSC Infinity and Mt. Rainier when compared to a Halo Ring.

Structure[edit]

Concept explorations for the construction of a Halo ring.
The foundational latticework of a Halo installation.

The Halos encountered in the modern times are 10,000 kilometers in diameter; this size is roughly similar to that of Earth, which is 12,756 km in diameter. While the original twelve Halos had a diameter of 30,000 kilometers,[69] concerns about their structural stability and transport led to the second series of rings being reduced in size.[33] The surface of each ring is 318 kilometers wide,[70] with a depth of 22.3 kilometers[71][72] to 47 kilometers.[11][Note 1] The overall circumference of the ring is 31,415 km and the interior surface area is 9,985,200 km2 - roughly the size of Canada.[11] The main structure of the ring is constructed of a superdense foundational material,[73] with elaborate scaffolding and cantilever structures laid over it to support the artificial landmasses and the myriad tunnel networks and caverns that riddle the installation's internal structure.[74] Many of these tunnels are transit conduits meant for use by the ring's Sentinels, though some of them can be traversed by humanoid beings.[75]

The Halo rings achieve their "gravity" through artificial gravity generators - despite their shape, the ring does not need to spin to create its gravitational pull, though they do spin for other reasons unrelated to gravity generation.[11] Due to this, the various Refugia present on the installation's surface may have different surface gravity, terrain, lighting and atmospheric conditions. These refugia are very modular and reconfigurable to support various types of life that are seeded on the rings.[11] When the UNSC Pillar of Autumn was detonated, it blasted a large mass from Installation 04; no longer a full loop, the centripetal force applied in much greater strength on the newly formed weak point, causing the ring to rip apart.[76]

A section of landmass being ejected from Installation 09.

The Halos are capable of repairing themselves to some degree, replacing damaged plates of foundation material and restoring biological sections.[77] Some of the 30,000 km-diameter Halos could also be reduced to a smaller size by shedding large portions of the foundation.[33] In order to prevent the ring from falling apart during this process, it could generate a hard light hub with spokes which hold each of the foundation plates in place.[78] However, the self-reduction process was far from perfect and made the original Halos prone to instability and collapse.[33] The newer Halos are capable of safely ejecting segments as well due to their modular and reconfigurable construction,[11] as long as the process is overseen by a capable enough intelligence such as a monitor.[58] Additionally, small, specifically defined parts of the Halos' terrain (along with the underlying foundation layers) can be jettisoned into space as a precautionary measure against Flood outbreaks.[60][79] In time, the ecosystems of these ejected sections can be restored by the Halos' automated systems.[79]

Halos also possess hard light reinforcement to stabilize and protect them against tidal and gravitational forces from other objects.[80] One of the most extraordinary systems possessed by the Halos (at least the twelve original rings) is their ability to lock entire sections of the ring, or, if necessary, the entirety of it, into reflective slipspace stasis. This suspends these sections in time and renders them invulnerable to damage from the outside, but consumes an enormous amount of energy.[81]

Each installation in the final Halo Array orbits a large, dense planet—most commonly a gas giant—which serves as a gravitational anchor.[15][11] For example, Installation 04 and Installation 05 orbited Threshold and Substance, respectively, which are both large gas giants, while Installation 03 is anchored to a large rocky planet.[16]

Custodial[edit]

343 Guilty Spark, monitor of Installation 04.

The installations are designed to be run by advanced artificial intelligence constructs specially assigned by the Forerunners. The highest intelligence on each installation is a single monitor.[82] The monitor's task is to ensure that the installation's Sentinels, which range from Constructors to Aggressors and Enforcers, repair, maintain, and defend the ring from damage, contain Flood specimens, and ensure that their own installation is ready to fire on demand, including running activation simulations.[7] In the event that a Halo Ring is destroyed, Tragic Solitude, Custodian of Installation 00 had the authority to assign a monitor to a ring. However, because Tragic Solitude was destroyed, Installation 09 was not assigned a monitor to oversee it.[11] Monitors also have access to their respective installation's defensive system.[83] Monitors are also permitted to make alterations to the Halo ring, as seen with 343 Guilty Spark ejecting sections of the ring during his time on Installation 04, as long as they do not interfere with primary functions of firing the Halo. Another instance of alterations made was with Installation 08, which would not be identical in every physical characteristic to Installation 04, as 343 Guilty Spark had made modifications and changes to the ring prior to its activation.[11]

The Sentinels encompass a broad category of less intelligent constructs which serve virtually any purpose necessary to ensure that the Halo functions properly and are capable of combating small Flood outbreaks. Should a major Flood outbreak occur, heavier automatons, such as the Enforcers and Sentinel Majors will be created. In the meantime, Constructors are also created to ensure that the Forerunner structures on the Installation are kept in optimal shape, and that they are not damaged by conflict or weather.[84]

Save for the monitor, all automatons can be constructed at specialized production facilities that float high in the Halo's atmosphere. They seem to have access to copious amounts of materials for constructing an almost indefinite number of automatons.

Environment[edit]

An environment on Installation 05.

Although first and foremost designed as weapons of mass destruction, the Halos are also designed as habitats for transplanted lifeforms, including but not limited to humans. After Master Builder Faber's plans were co-opted by the Librarian, the Halos were given terrestrial surfaces to support cataloged specimens. The Master Builder intended to allow these specimens to be infected by Flood forms contained on the rings, and then subsequently terminated in order to test the Halos' effectiveness.[12] The Halo installations support a wide range of environments, habitats, ecosystems, and climates. Installation 04 and Installation 05 supported warm, temperate forests[85] that were both deciduous and coniferous, swamps, and cold, snow covered tundra environments.[86][87] Installation 00 had climate ranging all the way from tundra,[88] to forest,[88] to desert.[89]

While the terrain of a Halo ring may appear to be naturally formed at first glance, it is actually artificially constructed. Strato-Sentinels extract raw materials from the source, process them in transit, and deposit building materials at the Installation.[90] Four huge terraforming factories then move across the face of the installation to "skin" it with landmasses and bodies of water. These factories also hold in the ring's nitrogen-oxygen atmosphere, which is then leaked out to the surface, eventually pouring through the superstructure, and tugged in place by centripetal force;[91] massive walls lining both sides of the ringworld prevent the atmosphere from leaking out into space.[92]

An intricate layer of metallic panels is laid down several meters below the surface of the terrain, upon which rock, soil, and eventually vegetation is added. Slopes, hills and mountains can be created by sculpting these panels.[74] Some features, such as landslides, are the result of time, and have been formed naturally. Others, such as the frigid conditions of the Quarantine Zone or the lake near the Temple on Installation 05 were artificially created.[93] There are also numerous indigenous life-forms that live on the Halos; these were brought on the installations as part of the Lifeworkers' conservation project. The structures seen on the surface of the installations are built as part of the underlying structure, with the terrain then "printed" on top of them, creating the appearance of structures built into the surrounding landscape when the inverse is in fact true.[11]

Facilities[edit]

The Control Room of Installation 04.

Each Halo has several assets that are uniform to all installations. Each contains a control room located somewhere upon its inner surface. The control room houses the installation's mainframe, known as the Core, from which all of the Halo's systems can be operated. The Halo's main weapon can be activated inserting the Activation Index into the Core; on the other hand, the Core may also be used to disable the main weapon.[60] Each Halo also possesses a Library, a large structure protected by an energy shield and a massive wall, where the Index is housed and protected by Sentinels.[14][84] The index itself is a semisolid holographic representation of the data needed to activate the ring, and can only be directly inserted successfully by a Reclaimer.

Installations also possess Cartographer facilities, which contain the complete, real-time record and schematic of the installation,[94] including its inner passages and networks, to be used as a navigational reference for traversing the installation. Flood containment and research facilities are also standard, used by the installation's monitor to conduct research on and observe the surviving Flood specimens; these are protected by Sentinels to prevent an outbreak.[95]

Transportation[edit]

Installation 09 exiting slipspace transit.

Facilities of the Halo Array contain advanced teleportation grids, allowing instantaneous transportation for a Monitor or Reclaimer to any place on the installation. Under normal circumstances, these grids cannot be accessed by the Flood, though the Gravemind was able to use that of Installation 05 by controlling 2401 Penitent Tangent.[7] For Sentinels, the installation is riddled with tunnel and cave networks for access and transportation.[95] Teleportation grids make use of unmediated slipspace cores bound to them that generate stable, pre-computed slipspace routes between synchronised endpoints. Due to the fact that these devices have fixed endpoints (such as across an installation or its immediate vicinity), destination flexibility is sacrificed for safety, speed, and security.[96][7]

The Halo installations are also equipped with drive engines spaced along their rim.[11] In the event of an emergency, a Halo can maneuver itself to avoid damage from a collision or weaponry.[97] While ideally moved through fixed portals, the rings are able to perform slipspace jumps under their own power. In the case of at least the original twelve rings, a failsafe measure implemented in the event of capture by hostile forces would transition the Halo into slipspace and place it on a collision course with a planet or other celestial body, ensuring the weapon's destruction rather than allowing it to fall in the wrong hands.[98] At the moment of Installation 04's destruction, at least one major fragment of the ring was moved into slipspace, likely as part of a similar failsafe.[99]

Firing method[edit]

Installation 05 as it aborts its firing sequence during the Battle of Installation 05.

The seven installations in the final Halo Array function via form of lethal radiation designed to kill all sentient life in the installation's three-dimensional radius of 25,000 light-years; when fired in concert with the rest of the Array, this sterilizing effect covers the entire galaxy.[100][101]

When activated, the Halo rings release a burst of cross-phased supermassive neutrinos.[9] The burst possesses a harmonic frequency, which can be tuned to destroy the nervous system of any macroscopic organism that possesses one, even one as rudimentary as a notochord, as shown in the aftermath of a low-powered test firing of a Halo performed by Mendicant Bias in the system of Charum Hakkor. Fine tuning the pulse can also allow for selective extermination of lifeforms with varying degrees of neural complexity.[102] The Halo effect is able to target and eliminate most forms of neural structures, from biological nervous systems to esoteric neural physics constructs, although the effect does not extend to artificial intelligences.[103] It has been noted that neoteric array is capable of killing life with the neurological complexity above that of a bumblebee approximately.[11] Simpler life forms that do not possess a neural system, such as microbes, fungi, algae, mosses, and traditional plants are unaffected.[104] While organisms aboard the twelve older rings were safe from the Halo effect itself due to its directional nature, any sentient being would still experience an uncomfortable sensation in the vicinity of the pulse.[105] The semi-directional pulse of the senescent rings allowed for localised cleansing of star systems and clusters.[11] Any living creature on the newer seven rings, however, would be killed and need to be reintroduced following the firing of the array. Furthermore, a key difference in the firing of the senescent and neoteric array is that the latter targets higher orders of life that are more complex neurologically, whereas the former will target and kill all life, which would lead to a complete collapse of planetary ecosystems as even insects are targeted. [11]

Like virtually all Forerunner technology, the Halos are powered by vacuum energy. When the main weapon is fired, vacuum energy is siphoned from local space-time to near-depletion.[34] The pulse of the main weapon is amplified by a series of phase pulse generators and channeled toward the Halo's center. A concentration of energy collects into the hub of the installation, which, when the weapon is fully charged, blasts outward in all directions.[101]

The radiation is propelled at superluminal speeds and will eventually propagate at a near-infinite velocity. This was known to generate causal paradoxes when the rings first fired, with two of the Halos reporting pre-echoes of the combined activation before the rings had been fired.[39] Once activated from Installation 00, all installations will cumulatively trigger one another as their radiation fields intersect, amplifying the effects of each individual Halo.[41] The energy discharge covers the Array's effective range and cleanses it of all affected sentient life.[101] Individual Halos can also be fired independently from the rest of the Array; this is known as a "tactical pulse".[24]

In the event a Halo's activation is canceled, a burst of energy is fired from the control center into the hub, causing the energy collected there to violently implode, then dissipate harmlessly.[13]

The final Halo Array, comprising the six smaller Halos (and the reduced Installation 07) were designed to fire in all directions, within a spherical radius of 25,000 light-years;[19] together, the rings were capable of killing all sentient life within three radii of the Milky Way's center.[19] The original twelve Halos were designed to fire laterally, generating a cone-shaped field with a maximum effective range of hundreds of thousands light-years. When fired from the greater Ark to the Large Magellanic Cloud, the blast was wide enough to cover the entire 14,000 light-year-wide satellite galaxy.[37] The rings could also be fired on a lower power setting, cleansing specific planets or systems within a relatively small area of effect.[104]

Effects[edit]

A creature is killed by the activation of the Halo Array and is instantly decayed by the Lifeworker solvent.

The nervous systems of all beings are targeted by the Halos and destroyed, rendering them useless to the Flood; however, the Halo effect does not disintegrate biomass, leaving the victims' bodies mostly intact.[106] Left untreated, lifeforms killed by the pulse will decay in great masses, which could lead to ecological devastation spread by a miasma of rotten biomatter. Therefore, Lifeworkers sprayed target biospheres with a solute that would cause any animal killed by the Array to instantly decay into its component molecules,[107] resulting in flash-desiccation.[101] Due to the Forerunners' use of solute, 21st century paleo-archeological studies gave no indication of the mass extinction caused by the Array's firing. However, in 2332 the Ross-Ziegler Blip revealed a tiny aberration in Earth's fossil records.[108]

The only known ways to avoid the effects of the pulse are to seek shelter in a shield world or to escape outside the range of the Array.[13] However, the effects can be nullified by using a ring in an incomplete state. When Installation 08 was fired in an incomplete state, John-117 survived aboard the UNSC Forward Unto Dawn, the Covenant Loyalists survived aboard Anodyne Spirit, and native animals on Installation 00 also survived the firing. Flood aboard High Charity also survived the firing, but Installation 00's Sentinels were able to contain those that survived with a containment shield around the ruined structure.

Halo Installations make use of Composer technology to an unknown degree as part of their firing.[11]

Protocol[edit]

Main article: Containment protocol

Each Halo ring can be activated individually by a Reclaimer, also placing the other installations in standby mode, or they can all be activated simultaneously from Installation 00. In the event of a major Flood outbreak, an installation's monitor will seek out a Reclaimer if available, whom they will enlist to aid them. It will teleport them to the installation's Library and will assist the individual in retrieving the Index. The monitor then stores the Index within its data arrays for safe transportation, lest the Reclaimer fall prey to the Flood before they can activate the installation. Once at the control room, the Reclaimer is given back the Index and must insert it into the Core in order to begin the activation sequence. At any point during the charging sequence, a Reclaimer is able to abort the firing by removing the Index from the Core.[13]

Defenses[edit]

Each Halo ring has its own defenses, though Sentinels from Installation 00 are always deployed at a newly constructed ring to finalize preparations to launch it. Retriever Sentinels are also stored inside the rings and will deploy automatically to attack anything deemed a threat.[109] The threat of the Sentinel defenses of Installation 03 were cause for Ivanoff Station to keep a permanent complement of Broadsword fighters and Mark 2551 Onager defense cannons on hand at all times, to ensure the station's defense.[110] The exterior band of Halo installations contains a series of Confidence-class weapon arrays, which can be used to enforce an exclusion zone of up to one light-year. UNSC Pillar of Autumn was initially tagged as a hostile by 343 Guilty Spark using Installation 04's Confidence-class defense system, but was given clearance after scans revealed that humans were aboard.[111][112]

List of installations[edit]

Prototypes[edit]

Name Location Monitor Status
Miniature Halo installation Hidden sector of the galaxy in orbit of a rogue planet None Destroyed

Senescent Array[edit]

Name Location Monitor Status
Greater Ark Extragalactic space Offensive Bias Destroyed
Gyre 01 N/A N/A Destroyed
Gyre 02 N/A N/A Destroyed
Gyre 03 N/A N/A Destroyed
Gyre 04 N/A N/A Destroyed
Gyre 05 N/A N/A Destroyed
Gyre 06 N/A N/A Destroyed
Gyre 07 N/A N/A Destroyed
Gyre 08 N/A N/A Destroyed
Gyre 09 Orbiting the greater Ark N/A Destroyed
Gyre 10 N/A N/A Destroyed
Gyre 11 N/A 117649 Despondent Pyre (formerly) Changed into Installation 07
Gyre 12 N/A N/A Destroyed

Neoteric Array[edit]

The installations in the neoteric[10] Halo Array are numbered in the order they were built in,[10] while their alphabetical designations were assigned in the order in which they were fired, with Alpha Halo being the first ring to fire.[113] Although Installation 07 was originally constructed as part of the first series of larger Halos, it was the last ring to be added to the neoteric Array while being heavily modified to suit its new role, hence the designation.[114]

Designation Name Location Monitor Status
Installation 00 Lesser Ark Extragalactic space 000 Tragic Solitude (destroyed) Heavily damaged, then repaired; contested between the Banished and the UNSC Spirit of Fire
Installation 01 Beta Halo Auric orbit, Myung system[115], Orion Arm[116] 001 Shamed Instrument Intact
Installation 02 Epsilon Halo Taphro orbit, Zhagolin system[117], Norma Arm[116] 007 Contrite Witness Intact
Installation 03 Gamma Halo Doavyn orbit, Khaphrae system, Scutum-Centaurus Arm[116] (formerly) 049 Abject Testament (missing) Major surface damage; control room ejected and destroyed
Installation 04 Alpha Halo Threshold orbit, Soell system, Orion Arm[116] 343 Guilty Spark (absent) Destroyed; wreckage under joint UNSC-Swords of Sanghelios quarantine per the Treaty of 2552 preventing the return of either faction
Installation 05 Delta Halo Substance orbit, Coelest system, Norma Arm[116] 2401 Penitent Tangent Surface glassed; under joint UNSC-Swords of Sanghelios quarantine
Installation 06 Kappa Halo Haakuth orbit, Mdorkon system[118], Perseus Arm[116] 16807 Abashed Eulogy Intact
Installation 07 Zeta Halo
Gyre 11 (Originally) 		Unknown (currently)[64][67]
Ephsu I orbit, Ephsu system, Sagittarius Arm[116] (formerly) 		117649 Despondent Pyre (destroyed)
Adjutant Resolution 		Damaged, controlled by the Banished
Replacements[edit]
Designation Original Name Location Monitor Status
Installation 08[119] Installation 04 Alpha Halo (replacement) Destroyed over Installation 00 343 Guilty Spark (absent) Destroyed
Installation 09[119] Installation 04 Alpha Halo (replacement) Between Installation 00 and the Soell system None Controlled by the Created

Non-canon and dubious canon appearances[edit]

Fractures: Entrenched[edit]

An image used for the Fracture notice.
 This article contains information from the Entrenched Fractures universe, and is not a part of the established Halo canon. To learn more information about the Entrenched universe, see its article.

On November 3, 67 AP, the Covenant captured the Project: PERPETUA's factory complex and wanted to launch the SCS Perpetua, in an attempt to arrive into a Halo ring and release the "Old Ones". However, the Sky Marshals, led by Commander Kolby and Aiken managed to capture and launch the Perpetua. Unknown to the Sky Marshals, the Covenant warped the Perpetua's atomic reactor with a Halo ring as a pre-defined destination.

On December 9, 67 AP, the SCS Perpetua, alongside the surviving Sky Marshals arrived into the 30,000-kilometer Halo ring, which was anchored into a green-brown planet. After thinking on Commander Kolby's sacrifice, Aiken ordered the star-zeppelin to begin its approach to the ring's surface.

Silver Timeline[edit]

HTV-SilverTeam logo.png
 This article contains information about the Silver Timeline, and is not a part of the established Halo canon.
Halo in Season 2 of Halo.
Halo in Halo: The Television Series Season Two.

The Covenant sought to locate Halo using the keystones, one of which was located on Madrigal[120] and the other on Eridanus II.[121]

After Silver Team recovered the Madrigal keystone which responded to John-117's touch, John learned from Reth that the Covenant were after the ring that the keystone displayed a weapon that was the end of all life as they knew it.[122] Miranda Keyes and Kai-125, by translating a Covenant transmission, discovered that they were seeking a Sacred Ring called Halo.[123]

When John used the Madrigal keystone, following Makee's advice not to fight the visions from it, he and Makee were briefly transported into a vision of them standing on the surface of a Halo ring.[124]

In order to help Makee convince Var 'Gatanai to go rogue, Cortana showed him John's memory of the surface of Halo. At the same time, Halsey implored John to focus on finding Halo, believing that its secrets were the key to humanity's survival.[125] Cortana later came up with the idea of using the stars in Halo's sky from the vision to determine its location, but it would require John and Makee touching the keystones at the same time in order to access the vision again. Cortana warned John that the Covenant were very close to finding Halo, that they were going to use it, and that they were almost there.[126] After communicating with John in the vision, Makee was able to use the stars to pinpoint the Halo's location which turned out to be Installation 04 in the Soell system.[127]

By tracking Makee's ship, ONI was able to find Installation 04's location. The ring gave off a powerful energy signature that distorted their star map. When John arrived at Halo, he found the First Fleet of Solemn Accord chasing Makee towards the ring while the SPARTAN-IIIs under Kai's command prepared to undertake a possible suicide mission that would destroy both the Covenant and UNSC fleets along with the star system and the Halo.[127]

Trivia[edit]

Main-Superintendent.png Browse more images in this article's gallery page.
  • The Halos are remarkably similar to the eponymous megastructure of Larry Niven's Ringworld series. However, Niven's Ringworld encircles a large star, whereas the Halos merely orbit planets, being much smaller than the former. The Halos are also very similar to the Orbitals from Iain M. Banks' Culture series, though considerably smaller.
  • In a Halo: Combat Evolved prototype, Installation 04 had a section that was only partially constructed. This feature was dropped from the final game, though it inspired the design of Installation 08.
  • The Prophet of Mercy once referred to the Halo Array's pulse as a divine wind.[84] This is a literal translation of kamikaze, suicide attacks carried out by Japanese pilots against Allied vessels near the end of World War II. Kamikaze aviators were willing to give their lives based on their fanatical devotion to defend Emperor Hirohito and the state. This is mirrored by the Covenant's quest to activate the Halos and commit holy war in deference to their gods.

Gallery[edit]

Concept art[edit]

  • Concept art of a Halo's surface for Halo 2: Anniversary's terminals.

    Concept art of a Halo's surface for Halo 2: Anniversary's terminals.

  • Concept art of a Halo ring firing upon and destroying Doisac for Halo Infinite.

    Concept art of a Halo ring firing upon and destroying Doisac for Halo Infinite.

  • Concept artwork of a Halo ring dream sequence for Halo: The Television Series.

    Concept artwork of a Halo ring dream sequence for Halo: The Television Series.

  • Concept artwork of a Halo ring dream sequence for Halo: The Television Series.

    Concept artwork of a Halo ring dream sequence for Halo: The Television Series.

  • Concept artwork of a Halo ring dream sequence for Halo: The Television Series.

    Concept artwork of a Halo ring dream sequence for Halo: The Television Series.

  • Concept artwork of a Halo ring dream sequence for Halo: The Television Series.

    Concept artwork of a Halo ring dream sequence for Halo: The Television Series.

  • Concept artwork of a Halo for Halo: The Television Series Season Two.

    Concept artwork of a Halo for Halo: The Television Series Season Two.

  • Concept artwork of a Halo for Halo: The Television Series Season Two.

    Concept artwork of a Halo for Halo: The Television Series Season Two.

Illustrations[edit]

Screenshots[edit]

List of appearances[edit]

Notes[edit]

  1. ^ The depth laid out in Halo: The Fall of Reach lists the ring's thickness as 22.3km, while the Lore Stream conducted by 343 Industries lists a depth of 47km. It is possible this disrepancy comes from the inclusion (or lack thereof) of the outer walls keeping the atmosphere in.

Sources[edit]

  1. ^ Halo: Combat Evolved, campaign level Two Betrayals
  2. ^ Halo: Warfleet, p. 92
  3. ^ Halo 3, Terminal Four
  4. ^ Halo: Combat Evolved Anniversary, Terminal Two
  5. ^ Halo: Combat Evolved, campaign level The Truth and Reconciliation
  6. ^ Halo: The Flood, page 38
  7. ^ a b c d Halo 2, campaign level Gravemind_(level)
  8. ^ Halo: The Flood, page 193
  9. ^ a b c d Halo: Cryptum, page 274
  10. ^ a b c d Reddit, Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS (Retrieved on Sep 18, 2017) [archive]
  11. ^ a b c d e f g h i j k l m n o p YouTube - HALO, Halo Lore Stream: The Halo Array (Retrieved on Apr 6, 2018)
  12. ^ a b Halo: Cryptum, pages 313, 334
  13. ^ a b c d e f Halo 2, campaign level The Great Journey
  14. ^ a b Halo: Combat Evolved, campaign level The Library
  15. ^ a b Halo: Silentium, page 237
  16. ^ a b Halo 4, campaign level Composer_(level)
  17. ^ Halo 2, campaign level The Oracle
  18. ^ Halo: Combat Evolved Anniversary, Terminal 8 ("25,000 light years. That is the effective range of this installation.")
  19. ^ a b c Halo: Combat Evolved, level Two Betrayals, 343 Guilty Spark: "Technically, this installation's pulse has a maximum effective radius of 25,000 light years."
  20. ^ Halo: Combat Evolved, level The Library, 343 Guilty Spark: "Why the Flood is, naturally, simply too dangerous to release, and mass sterilization protocols may again need to be enacted."
  21. ^ Halo: Cryptum, page 132
  22. ^ a b Halo: Rebirth
  23. ^ Halo Waypoint, Introducing Halo Wars 2: Awakening the Nightmare: "While most of the Flood threat was destroyed in the crash of High Charity and in the explosive end of Halo 3, even the smallest remaining spore of Flood can take over the galaxy, given enough time." (Retrieved on Sep 29, 2021) [local archive] [external archive]
  24. ^ a b Halo 3, campaign level The Covenant: "343 Guilty Spark: "The Ark is out of range of all the active installations!""
  25. ^ Halo: Ghosts of Onyx, page ??
  26. ^ Halo: Cryptum, page 243
  27. ^ Halo: Shadow of Intent, pages 5-10 (Google Play edition)
  28. ^ a b Halo: Silentium, page 44
  29. ^ Halo: Primordium, page 188-190
  30. ^ Halo: Cryptum, page 329 ("Slowly it dawned on me that I was looking upon another array of installations: six rings, each rising from one of the petals of an enormous flower.")
  31. ^ Halo: Silentium, pages 250-251
  32. ^ Halo: Silentium, page 45
  33. ^ a b c d Halo: Silentium, page 91
  34. ^ a b c Halo: Silentium, page 270
  35. ^ a b c Halo: Silentium, page 314
  36. ^ Halo: Silentium, pages 234, 237
  37. ^ a b Halo: Silentium, page 273
  38. ^ Halo: Silentium, page 313
  39. ^ a b Halo: Silentium, pages 326-327
  40. ^ Halo: Silentium, pages 322-323
  41. ^ a b Halo: Silentium, page 312
  42. ^ Halo Infinite: Audio logs
  43. ^ "Conversations from the Universe"
  44. ^ Halo: Combat Evolved Anniversary, Terminals 5-6
  45. ^ Halo 2, multiplayer level Burial Mounds
  46. ^ Eleventh Hour reports - #5
  47. ^ Halo: The Essential Visual Guide, page 14
  48. ^ Halo: Hunters in the Dark, Chapter 2
  49. ^ Halo: Glasslands, page 50
  50. ^ Halo: Primordium
  51. ^ Halo: Hunters in the Dark
  52. ^ a b Halo Wars 2, campaign level Hold the Line
  53. ^ Halo: Nightfall
  54. ^ Halo Wars: Phoenix Logs
  55. ^ Halo 4
  56. ^ Halo: Spartan Strike, campaign level Operation C: Valiant Hammer
  57. ^ Halo: Escalation: Issue 9
  58. ^ a b Halo: Escalation: Issue 10
  59. ^ Halo Wars 2, campaign level The Signal
  60. ^ a b c Halo Wars 2, campaign level Last Stand
  61. ^ Halo: Shadows of Reach
  62. ^ Halo Encyclopedia (2022 edition), page 247
  63. ^ Halo: Divine Wind
  64. ^ a b Halo Infinite, Database: Outpost Intel 09 - To Andrew Valleros
  65. ^ Halo: The Rubicon Protocol, chapter 4
  66. ^ Halo: The Rubicon Protocol, chapter 30
  67. ^ a b Halo: The Rubicon Protocol, chapter 13
  68. ^ Halo Infinite
  69. ^ Halo: Cryptum, page 310
  70. ^ Halo: The Essential Visual Guide, page 6
  71. ^ Halo: The Fall of Reach, page 339 (2001)
  72. ^ Halo: The Flood, page 13 (2003)
  73. ^ Halo: The Flood, page 340
  74. ^ a b Halo 3, campaign level Halo_(Halo_3_level)
  75. ^ Halo: Combat Evolved, campaign level Halo
  76. ^ Halo: Combat Evolved campaign level, The Maw
  77. ^ Halo: Primordium, page 77-78
  78. ^ Halo: Primordium, pages 345-346
  79. ^ a b Halo: Combat Evolved Anniversary, Terminal Four
  80. ^ Halo: Cryptum, page 311
  81. ^ Halo: Primordium, page 331-332
  82. ^ Halo: Combat Evolved, level 343 Guilty Spark
  83. ^ Halo: Combat Evolved Anniversary, Terminal 1
  84. ^ a b c Halo 2, level Sacred Icon
  85. ^ Halo 2, level Uprising
  86. ^ Halo: Combat Evolved, level Assault on the Control Room
  87. ^ Halo 2, level Quarantine Zone
  88. ^ a b Halo 3, level The Covenant
  89. ^ Halo 3, level The Ark
  90. ^ The Art of Halo 3, page 30
  91. ^ The Art of Halo 3, page 116
  92. ^ Halo: Primordium, pages 40, 148
  93. ^ Halo 2, campaign level Delta Halo
  94. ^ Halo: Primordium, page 295
  95. ^ a b Halo: The Flood, pages 240-242
  96. ^ Halo: Warfleet, p.11
  97. ^ Halo: Cryptum,, page 314
  98. ^ Halo: Primordium, pages 279, 339
  99. ^ Halo Waypoint: Alpha Shard
  100. ^ Halo Encyclopedia (2009 edition), pages 170-174
  101. ^ a b c d Halo: Combat Evolved Anniversary, Terminal Eight
  102. ^ Twitter: Jeff Easterling on Twitter
  103. ^ Halo: Silentium, page 310
  104. ^ a b Halo: Cryptum, pages 131-133
  105. ^ Halo: Silentium, pages 272-273
  106. ^ Halo 3, Terminal 6 ("I toss around [37,654 tonne] dreadnoughts like they were fighters; dimly aware of the former crews being crushed to liquescence.")
  107. ^ Halo: Silentium, String Two
  108. ^ Halo: Evolutions - Essential Tales of the Halo Universe, "From the Office of Dr. William Arthur Iqbal", page 519
  109. ^ Halo Wars 2, campaign level, The Halo
  110. ^ Halo: Warfleet, Space Stations, pages 34-35
  111. ^ YouTube: Halo Lore Stream: The Halo Array
  112. ^ Halo: Combat Evolved Anniversary Terminals
  113. ^ Halo: Silentium, p. 327
  114. ^ Reddit: Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS (comment by GrimBrotherOne)
  115. ^ Halo Encyclopedia (2022 edition), page 345
  116. ^ a b c d e f g Halo: Warfleet, p. 12-13
  117. ^ Halo Encyclopedia (2022 edition), page 347
  118. ^ Halo Encyclopedia (2022 edition), page 349
  119. ^ a b Reddit: Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS "Sorry, 08 and 09 make way more sense :-) In actuality, they aren't meant to directly replace an individual ring, but to replace the loss in coverage that ring offered the galaxy.", Jeff Easterling
  120. ^ Halo: The Television Series, episode Contact
  121. ^ Halo: The Television Series, episode Emergence
  122. ^ Halo: The Television Series, episode Unbound
  123. ^ Halo: The Television Series, episode Homecoming
  124. ^ Halo: The Television Series, episode Solace
  125. ^ Halo: The Television Series, episode Aleria
  126. ^ Halo: The Television Series, episode Onyx
  127. ^ a b Halo: The Television Series, episode Thermopylae

See also[edit]

v • d • e
 
The Forerunners

v • d • e
 
Halo Array
Arks
Senescent array
Gyre 01 • Gyre 02 • Gyre 03 • Gyre 04 • Gyre 05 • Gyre 06 • Gyre 07 • Gyre 08 • Gyre 09 • Gyre 10 • Gyre 11 • Gyre 12
Neoteric array
Other

v • d • e
 
Installation components

v • d • e
 
Other installations
Other megastructures
Other facilities
For a complete list, check out our Forerunner category.
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