List of unidentified species

A look at a crashed vessel from an unidentified species, responsible for landing on Installation 04.

During its history, the Milky Way galaxy has played host to many intelligent forms of alien life. While many can be grouped under the wider banners of the Forerunner Ecumene, the Covenant empire or the auspices of the Unified Earth Government for humanity, many alien encounters have been recorded with no currently-known species responsible.

Overview

Forerunner indexing

According to a Catalog, before the firing of the Halo Array on 97,445 BCE, the Librarian studied and favored at least 123 species across three million worlds in regions the Forerunners explored in the Milky Way galaxy. The Catalog was uncertain however how many the Librarian aimed to preserve. While many sentient species were ultimately indexed and reintroduced, many of them did not reach Tier 7 of the Technological Achievement Tiers after the firing of the Halo array, where only a handful were encountered by Humanity in the Orion Arm of the galaxy, and not every species that were in the Covenant were cataloged by the United Nations Space Command, with even the Covenant client species keeping few records of their affairs with them.

Locations

Great dense cloud

Following the firing of the Halo Array, a final communication was heard by 343 Guilty Spark at Installation 04 from a "great dense cloud". This was sent from a species that just managed to send out their first communications out from their home system. This species was not encountered by the Forerunners or Flood; and ultimately was not indexed by the Librarian for reintroduction. Guilty Spark did not understand their message, but presumed it was hopeful signals. After the Halo's pulse hit the cloud, the communication stopped.

Installation 04 (Alpha Halo)

Over its operational lifespan, several unidentified visitors have found their way to Halo Installation 04.

Crashed ship

Main article: Unidentified alien vessel

Around 40,000 BCE (50,000 years following the firing of the array), an unidentified alien vessel crashed on the ring during an experiment 343 Guilty Spark conducted on the Halo. None of the ship's occupants attempted to leave the vessel's crash site or attempt contact, leading Guilty Spark to build a sarcophagus around the vessel. Ultimately, the Monitor was hopeful for the next species to arrive on the ring.

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  Unidentified ship.

Visitors to the ring

During the Battle of Installation 04, 343 Guilty Spark noted in logs made during the battle that the Covenant landing on the ring and seeking something was similar to another alien species who previously arrived at the ring, recorded what they saw and left. These visits ultimately lead to 343 Guilty Spark changing his excitement at the prospect of meeting an alien species to defensive; threatening ships that trespassed near the ring including the UNSC Pillar of Autumn in 2552.

Installation 05 (Delta Halo)

It has been suggested that outside meddling may have caused the breach which lead to a Flood outbreak at the installation's containment facility, culminating in the outbreak and eventual formation of a Gravemind on Installation 05.

System of Miasmic Giants

Around 851 BCE, the Sangheili 'Crecka recalled a event that happened "many cycles ago" in the System of Miasmic Giants where a hostile species attacked a vessel he served on. During the attack, 'Crecka was the last survivor and managed to escape by piloting the ship randomly though slipspace. According to 'Crecka, the species did not speak a civilized tongue.

The Refuge

According to Bal'Tol 'Xellus, an alien prisoner from a far off planet found The Refuge, where it taught 'Xellus' ancestors a meditation that would be passed on for generations until it was passed onto them.

Line Installation 9-12

Among the debris found at Line Installation 9-12 includes a number of ships belonging to species not known to be Human or Covenant client species.

Netherop

Main article: Netherop species

During the time of the Forerunner-Precursor war, the planet of Netherop hosted a Tier 6 species. The species was assumed extinct by John-117.

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  Oath Warden Crei 'Ayomuu, Spartan-IV Olympia Vale, and Arbiter Thel 'Vadam among the ruins on Netherop.

Karava

This species was discovered by the Covenant on their homeworld of Karava. When encountered, they refused to give in to the Covenant's demands - resulting in the Covenant deploying 300 N'weo-pattern Gigas fighters against the species, wiping it out completely in a total genocide.

Unknown skycrypt

On a world that was controlled by the Forerunners, numerous skycrypts were constructed to keep threats contained. One of these platforms had a security breach leading to the inhabitant escaping.

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  A broken "window" on the confinement platform.

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  The confinement platform.

October 10 aggressors

Main article: Battle of October 10

On October 10, 2552 (ten days prior to the outbreak of the Battle for Earth), a series of twelve unknown starships entered the Sol system broadcasting outdated civilian IFF codes and were engaged by a UNSC Navy task force. Battle Group Rhino engaged the aggressors on October 10, with eleven immediately making unauthorised slipspace transits outside of the Sol system, and the single remaining vessel engaging. UNSC Totem Lake was lost with all hands in the battle after suffering numerous hull breaches and boarding actions, before Battle Group Rhino fell back to Phase Line Alpha, over Enceladus.

Underground species

A handful of lost burrowing species and mining civilizations across the Orion Arm had been discovered by humanity by 2559.

Gallery

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  Early concept for Halo Infinite depicting a large, armored unknown alien species with four arms and vaguely reptilian features.