Xalanyn

"If Halo cannot kill them, it must imprison them."

- Grand Edict to Despondent Pyre

The Xalanyn, also known as the Endless, was an advanced race, whose members was imprisoned by the Forerunners on Installation 07 by 97,368 BCE due to their ability to survive the effects of the Halo Array. Their cylixes were eventually discovered by Atriox during the Installation 07 conflict in 2560.

Background
The origins of the Xalanyn were unknown, but they were one of the sentient species that were extant during the fall of the Forerunner civilization. They were not indexed by the Forerunners prior to the firing of the Halo Array, and once the Halo rings were fired, they inexplicably survived. During the century after the firing, the Xalanyn were discovered alive and well by the Forerunners, much to the latter's confusion.

The Forerunners and the Xalanyn arranged a parley between delegates from the two species, with Installation 07 taken into range of the Xalanyn homeworld. The Forerunners deemed the Endless to be a threat and subjugated them for study at the Silent Auditorium on Installation 07. Eventually, the Forerunners decided that the Endless had to be sealed on the Ring perpetually. The Grand Edict charged Installation 07's monitor, 117649 Despondent Pyre, with guarding the Endless's prison, and assigned Offensive Bias to the ring to aid in this.

Return
"The Harbinger"

In 2560, the Banished forces under the leadership of its War Chief Escharum arrived at Installation 07. The Banished excavated Forerunner subterranean structures, eventually coming across the cylix that contained the Xalanyn known as the "Harbinger". The Harbinger was released from her cylix by forcing a human prisoner of war, Lucas Browning, to interface with her cylix. Upon her release, the Harbinger allied with Escharum. She promised to help Escharum return the ring to its operational status, while Escharm would help her release her fellow Xalanyn from the Silent Auditorium. Master Chief Petty Officer John-117 intervened, killing both in the process.

Elsewhere on the ring, cylixes of other Xalanyn, though with a different appearance compared to that of the Harbinger, was found by Atriox.

Physiology
The physiology of the Xalanyn appears to be highly variable, but a number of shared key traits are present in all forms seen so far. The species is generally humanoid in physical structure, possessing two arms and at least two legs, their hands bearing three or four digits. In contrast to other humanoid species, their feet project downward in a hyperextended position rather than forward, which renders the species incapable of terrestrial locomotion. As a result of this, the Xalanyn rely on the use of thrusters for movement. Their heads are smooth and hairless, with two wide-set pupil-less eyes, no nostrils, and a small, narrow mouth surrounded by a pair of fin-like tentacles. While their mouths contain teeth, they also possess a larger spike-like "tooth" at the front of their lower jaw.

List of appearances

 * Halo Infinite