Retriever Sentinel

This article is about a variant of Strato-Sentinels. For the other variant, see Steward Sentinel.

Retriever Sentinel
Overview
Role:	Construction and mining
Length:	484.0 meters (1,587.9 ft)
Width:	458.3 meters (1,503.6 ft)
Height:	118.1 meters (387.5 ft)
Propulsion:	Impulse drive
Armament:	Sterilization beam
Energy shielding:	Little to no energy shielding
Other systems:	Gravitic impeller Reconstitution emitters

"It's a Strato-Sentinel. It's one of the automated drones the Forerunners use on their artificial worlds. The Covenant originally thought them to be holy warriors of the Sacred Rings. There are many types of Sentinels that the Forerunners created—this particular one is designated as a Retriever."

— Usze 'Taham

The Retriever Sentinel, is a variant of Strato-Sentinel drones employed by the Forerunners. Considered to be one of the more powerful variants of the Sentinel, Retrievers are massive, ship-sized drones that were utilized to construct installations of the Halo Array from Installation 00, as well as to provide maintenance to the Ark itself.

Overview

Design details

Nathaniel Palmer and other scientists observe Retrievers operate on the Ark.

"Our records indicate that it employs an artificially produced gravitic force to remove minerals from a planet's surface. Those minerals in turn are used to build Forerunner structures and installations."

— Usze 'Taham, referring to the Retriever Sentinels

A Retriever is capable of producing an artificial gravitic force that allows it to remove materials from a world's surface. Once in position above an acceptable place to harvest, the Retriever deploys its blue, gravitic beam towards the world's surface and begins hauling chunks of land caught in the beam into its underbelly. The mining process utilized by a Retriever is noted to create a tornado-like effect as the ground is pulled into the Sentinel's hold. If deemed necessary, a Retriever is capable of connecting and merging with another Retriever and forming a single unit. Combined Retrievers somewhat resemble an average Retriever, though they seem to be more effective in combat and are significantly more maneuverable. With no apparent drawbacks, a combined Retriever seems to take on the benefits of both Retrievers' speed and weaponry.

When a Retriever is threatened or attacked, these Sentinels may use their gravitic beam as a dangerous and highly destructive, though cumbersome, weapon. As the Sentinel was not designed for combat situations, Retrievers have little to no shielding. In 2555, monitor 000 Tragic Solitude outfitted thousands of Retrievers with massive energy weapons mounted on their fronts. These weapons are similar in design to the Sentinel beams employed by the smaller Aggressor Sentinels. These Retrievers were capable of utilized powerful volleys of energy against opponents and were significantly faster and had greater maneuverability in space.

Role

"I thought Retrievers were just for mining and gathering minerals!"

— Captain Annabelle Richards, upon seeing a heavily armed Retriever

The Retrievers are among the most powerful of the Sentinels employed by the Forerunners, with their primary purpose being the mining, gathering, and transporting of minerals and other natural resources from a world. Using its artificially created gravitic force, Retrievers extract materials from a world's surface and transport to construct Forerunner structures and installations.

The Forerunners utilized Retrievers to help in the maintenance of Installation 00. The Retrievers employed at the Ark worked with Assembler Sentinels to construct new installations. Populating the Foundry, Retrievers mined and gathered raw materials from the planetoid hosted in Installation 00's center and transported them to a forge within the Foundry that refined, processed, and stabilized the materials into the mold of a Halo installation. The Assemblers would then use these resources to build components of the installations. Although usually automated, Retrievers can be controlled by a monitor. Monitors are capable of effectively utilizing Retrievers in combat, and can have them overwhelm opponents.

A Retriever is programmed to complete its tasks with no deviations or hesitations. Although the function of the Retriever is primarily construction-related, the Sentinel is able to defend itself, or its installation, if necessary. However, Retrievers maneuver poorly and are unable to effectively combat modern Sangheili and human vessels alone. Thus, Aggressor and Protector Sentinels are primarily used as defensive constructs on installations.

Variants

Multiple variants of Retriever have been seen in use across Forerunner megastructures.

• 

  The Retriever variant found on Installation 00.

• 

  Another variant of Retriever.

Operational history

Prehistory

Retriever Sentinels were utilized by the Forerunners to aid in the construction of the Halo Array at Installation 00, with the intentions of firing the rings to wipe out the Flood.

Conflict on the Ark

After the destruction of Installation 04 on September 23, 2552, Retrievers on Installation 00 began to mine the planetoid captured in the Ark's Foundry to construct a replacement installation. On December 11, 2552, these Retrievers were encountered and observed by Sangheili and United Nations Space Command forces during the Battle of Installation 00. The battle ultimately resulted in the Ark becoming heavily damaged, leading to 000 Tragic Solitude—Installation 00's now-rampant monitor—allocating all of his time and resources to the construction of thousands of heavily armed Retrievers that would mine human colonies for resources to repair the Ark, blaming humanity for damaging his installation.

In March of 2555, Tragic Solitude used a captured human to initiate the activation of the Halo Array. As expected by the ancilla, the United Nations Space Command and Swords of Sanghelios reopened the Portal at Voi on Earth to reach the Ark. With the portal now open, Tragic Solitude sent a Retriever through the portal to gather Earth's resources to repair Installation 00, which sustained heavy damages in the aforementioned battle. As the Retriever began to strip mine the country of Kenya, the cruiser UNSC Endeavor immediately responded by attacking the Sentinel. With the aid of several UNSC attack craft, Endeavor was able to destroy the Retriever. As the UNSC and Sangheili team prepared to venture into the slipspace portal aboard Mayhem, another Retriever suddenly exited—this time, heavily armed. However, the Sentinel was easily outmatched by Mayhem and was destroyed. When Mayhem entered the intergalactic space around the Ark, dozens of Retrievers attacked the corvette and managed to down the ship.

After the crew of Mayhem succeeded in averting the activation sequence of the Halo rings, Tragic Solitude sent his army of thousands of heavily armed Retrievers through the portal to Earth. Though the Huragok Drifts Randomly managed to seize control of the Ark from Tragic Solitude, the monitor kept the Retrievers under his personal control, keeping Drifts from stopping their deployment. The Retrievers exited the portal over Kenya and some proceeded to extract materials from Earth, while others immediately engaged the dozens of vessels from the UNSC Home Fleet that were awaiting outside the portal. While the Retrievers' lack of armor made them vulnerable to human fire, their vast numbers overwhelmed the Home Fleet. However, members of the crew of Mayhem fired into the data banks of Tragic Solitude and the monitor reluctantly called off the Retrievers to convince his attackers to stop. The Retrievers retreated back into the portal and returned to the Ark, upon receiving Tragic Solitude's signal. After Solitude's subsequent destruction, the thousands of Retrievers turned dormant, remaining adrift in the space around the installation without any monitor to guide them.

Human appropriation

Retrievers under the control of Ellen Anders.

"When we first arrived here, the Ark had suffered great wounds from our war against the Covenant, and so we activated dormant Retriever Sentinels and deployed them to strip-mine lifeless planets for the materials needed to repair the installation. Like watching a sleeping giant nudged into wakefulness, the reconstruction slowly reached full automation until we were no longer needed to guide the Sentinels and could simply sit back and record the wonder of a world being reborn."

— Nathaniel J. Palmer, an archaeologist of Henry Lamb Research Outpost

Doctor Luther Mann theorized that the dormant Retrievers could be reactivated and utilized to repair the Ark, opening slipspace portals to strip-mine uninhabited planets for the resources and minerals required to repair the Ark. In 2557, a human research team traveled to Installation 00 aboard Eden Rising to establish a permanent base on the Ark, the Henry Lamb Research Outpost. Desiring to repair the installation, the researchers activated the dormant Retrievers, under the guide and direction of the smart AI Isabel. To gain resources, the Retrievers were deployed to strip-mine lifeless planets. Before long, the Retrievers were able to enact repairs unsupervised, leading to Isabel and the researchers setting to the task of cataloging and analyzing the installation. The Retrievers acted quickly and within months had largely restored the Ark to its former state, as well as constructing another replacement Halo installation at the Foundry.

However, in October 2558, the portal to the Ark had shut down again with the Banished arriving at the installation in the following month. The human researchers were killed by the Banished, while the Retrievers sought to defend their installation from the hostile invaders who were attempting to appropriate the installation for their own purposes. In March 2559, UNSC Spirit of Fire arrived over the Ark, where the ship's crew soon came into conflict with the Banished. During the resulting battle, UNSC forces managed to access the replacement Halo installation, having it depart the Ark's Foundry. In response, heightened automated security protocols were initiated and Retrievers were deployed to repel the invaders. While Banished and UNSC forces battled on the surface of the new Halo, a Retriever attacked forces from both sides. After UNSC forces managed to damage the Sentinel, the Retriever retreated for repairs. With UNSC forces taking control of three nearby Control Towers, Professor Ellen Anders of Spirit of Fire soon found a way to manipulate the Ark's command codes and bypass directive locks, allowing her to take control of the Retriever. Anders was then able to use the Retriever's weapons to destroy the Banished shield generator blocking access to the Halo's Control Room

Retriever Sentinels also played a role in guarding Forerunner starfighters. Several protected the entrance of a Despair-class fighter hangar, attacking UNSC and Banished forces indiscriminately. After the cloaking shield was shut off, a Retriever attacked the UNSC forces who ultimately managed to destroy the Retriever, allowing them to see what was behind the cloaking field. With the Retriever gone, Major Elijah Vaughan and Sunray 1-1 were able to destroy the starfighter before the Banished could launch it to destroy the UNSC Spirit of Fire.

Second Ark Outbreak

Main article: Outbreak on Installation 00

Atriox later issued orders to Pavium and Voridus to salvage material from around High Charity's crash site for their ongoing campaign against the humans, warning them not to go beyond the containment shield. Two Retriever Sentinels were dispatched to stop the Banished from reaching the crash site which the Banished forces were unable to counter. However, Voridus managed to shut down the Sentinel defense network using a nearby terminal, disabling all Sentinel operations and causing the Retrievers to be destroyed. Ignoring Atriox's orders, Voridus breached the containment shield, releasing the Flood, which spread uncontrollably due to the Sentinels being disabled by the defense network.

With the Flood unleashed upon the Ark once again from High Charity's crash site, Voridus traveled into a nearby Forerunner archive and managed to reactivate the Sentinel defense network. As the Banished battled a Proto-Gravemind that was in danger of evolving into a Gravemind, it retreated to safety and refused to respond to Banished attacks, having grown too strong. As a result, Pavium and Voridus directed their troops to clear out a nearby Sentinel lock, summoning a Retriever. The combined fire of the Banished and the Retriever forced the Proto-Gravemind to expose its core and then finally destroyed the creature, allowing the Banished and the Sentinels to contain the Flood outbreak.

Gameplay

Halo Wars 2

• Info: Summons a powerful controllable Retriever Sentinel. Super Unit and Ultimate Unit for Sentinels.
• Tier: 0
• Cost: 24, 1,800, 1,800

In Halo Wars 2, the Retriever Sentinel is a Super Unit for Sentinels exclusive to Professor Anders that can only be built using a leader power. Unlike the G81 Condor or Barukaza Workshop Scarab, there can only be one Retriever Sentinel used by the player at a time. If the player picks the Retriever Unit leader power, Anders is able to deploy two types of Super Unit, the G81 Condor and Retriever Sentinel. In gameplay information, Retrievers are labelled as an Ultimate Unit.

During the fight on Installation 09 in the campaign, Anders is able to take control of a Retriever Sentinel that initially attacks both the UNSC and the Banished. In the campaign, the Retriever is indestructible after the player manages to damage it to 25% of its HP, forcing it to retreat and repairs. The player must avoid the Retriever until Anders can take control of it.

During Operation: SPEARBREAKER, the Retriever Sentinel is equipped with energy shielding and can call in Sentinel Swarms to repair itself. The player must destroy the nearby Aggressor Sentinels to dissipate the swarm and continue their attack.

During the Halo Wars 2: Awakening the Nightmare level What Could Go Wrong?, two Retriever Sentinels are dispatched to stop Voridus' Scarab and are dispatched once Voridus shuts down the Sentinel defense network at High Charity's crash site. In an attempt to destroy a Proto-Gravemind in the level Manifestation, Pavium reactivates the Sentinel defense network and clears a Forerunner launch site, which summons a Retriever Sentinel. This Retriever Sentinel falls under the control of the player and plays a vital role as its firepower is needed to kill the Proto-Gravemind.

Phoenix Log

Phoenix Log - Retriever Sentinel

Extremely powerful Forerunner drone The Ark's Retriever Sentinels are among the most powerful Forerunner drones, their primary purpose being the mining of the Foundry in the creation of Halos and Ark maintenance. However, like all Forerunner drones, they can also be used to defend the Ark by turning its sentinel lasers on anyone who threatens it. The Retriever Sentinels played an important part in repairing the Ark after the events of 2553 in the final battle between the UNSC and the Covenant. UNSC scientists at the Henry Lamb Research outpost reactivated the dormant retrievers and watched in awe as the Ark was restored to its former glories. Sadly, war has once again come to the Ark, but the Forerunner drones built to protect it will stand fast and push back against any and all invaders.

Gallery

Browse more images in this article's gallery page.

Development images

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  Concept art of the Retriever Sentinel for Halo Wars 2.

• 

  Artwork of Retriever Sentinels, Protector Sentinels, and Aggressor Sentinels moving to attack Decimus.

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  Artwork of Banished forces amidst the wreckage of a Retriever Sentinel.

• 

  A high-poly render of the Retriever Sentinel asset.

Screenshots

• 

  A Retriever Sentinel in Halo Wars 2.

• 

  A Retriever charging its fusion bolt attack.

• 

  A Retriever with a swarm of Protector and Aggressor Sentinels.

• 

  A Retriever and other Sentinels attack a Banished Banished outpost.

• 

  A Retriever Sentinel from the side.

• 

  A Retriever from behind.

• 

  A Retriever from the other side.

List of appearances

• Halo: Hunters in the Dark (First appearance)
• Halo Mythos (Mentioned only)
• Halo Wars 2
• Halo: Renegades (Mentioned only)