ONI Ilex Facility

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ONI Ilex Facility
Screenshot of Cliffhanger.
Facility information


Unidentified planet[1][2]


Historical information

In use:

Post-war era[3]

Controlled by:

Office of Naval Intelligence (formerly)[3][4]


The ONI Ilex Facility is a classified military black site formerly operated by the Office of Naval Intelligence as part of the Zeta Halo project.[3][4]



The Ilex Facility is located atop a frigid mountain on an unidentified human world. Several similar facilities can be seen on nearby mountaintops while large dish-like structures similar to spherical reflector radio telescopes are scattered throughout the mountain range's valleys.[1] Elevators lead down into the interior of the mountain where other research was once conducted on captured Covenant technology.[4]


At the center of the facility is a large spire with several smaller structures strewn around its base and set into the frozen mountainside. Just below the spire is a structure containing hexagonal devices reminiscent of Installation 07's hexagonal building blocks,[1] revealing the facility's involvement in the research of Forerunner technology.[1][2][3]


Covenant research[edit]

A screenshot of Illusion.
A subterranean Ilex Facility laboratory within the mountain.

The Ilex Facility was involved in experiments on Covenant active camouflage and overshield technologies. This resulted in the creation of the Multifunctional Emitter Prototype, a large device that can emit a field producing active camouflage or overshield effects.[4]

Forerunner research[edit]

The Ilex Facility also became involved in Operation: ECDYSIS, a facet of the ongoing study of Installation 07 by the United Nations Space Command.[3] Researchers here studied materiel and technologies discovered on the ringworld. Some of the structures analyzed at the Ilex Facility included structural samples taken from Installation 07, which were able to yield a number of discoveries in mineralogy. However, despite active research, the base was unable to replicate the effects of reformation as demonstrated on the ring, due to being unable to reproduce the method in which Forerunner technology turns raw materials into useful structures even despite a number of workarounds implemented to boost the base's electrical power output to a fraction of that needed for full-scale testing.[2][3]

Ultimately, the base's staff were unable to progress as rapidly in their understanding of Installation 07 as the researchers on the shield world Trevelyan were, though they remained hopeful that future discoveries may be able to assist humanity in restoring the multitude of colony worlds glassed by the Covenant during the Human-Covenant War.[3] However, the Ilex Facility would eventually become abandoned and fall into disrepair.[4]


The Ilex Facility is the setting of the Halo Infinite multiplayer maps Cliffhanger[3] and Illusion.[4]


Ilex, or holly, is a genus of flowering plants known for its bright red fruits.


List of appearances[edit]