Chi Ceti IV is a planet in the Chi Ceti system. The planet has a top-secret installation on its surface, known as the Damascus Testing Facility, where the SPARTAN-IIs were first given their Mark IV Mjolnir Armor during the Battle of Chi Ceti.
The facility and a UNSC training center was abandoned and, those being the only known Human installations on the planet, it is quite unlikely that the planet was destroyed and glassed by the Covenant ensuing the evacuation. When the Covenant attacked, the SPARTAN-IIs boarded their ship and succeeded in destroying it, but Samuel-034 died in the process, the first Spartan to be listed as MIA. The Mjolnir Powered Assault Armor/EOD variant and the Soldier variant of the Mjolnir Powered Assault Armor (GEN2) were also developed at the Damascus facility in this system.
The engagement taking place in the orbit of Chi Ceti IV between the UNSC Commonwealth and the Covenant light cruiser Unrelenting was one of the first, and perhaps also one of the smallest naval engagements to occur between Covenant and UNSC forces. But it was also perhaps one of the most notable engagements, due to the loss of the first Spartan, Samuel-034.
- A distant red nebula is visible from the system.
- A planet from Bungie's previous game, Marathon, takes a similar name, Tau Ceti IV.
- Tau Ceti IV was also where the Mjolnir Mark IV Cyborgs revealed themselves in Marathon.
- One of Chi Ceti's moons, Muroto, was home to the Materials Group mining facilities.
- According to Halo 4, the Soldier armor variant was developed on Chi Ceti IV. Thus meaning it was reoccupied by the UNSC during or after the Human-Covenant war.