From Halopedia, the Halo wiki
Idomenius was one of many Jiralhanae picked to serve in Truth's fleet at the conclusion of the Human-Covenant War. He served in the fleet during the Battle of Installation 00, and was a part of the force ordered to defend the keyship Anodyne Spirit. Alongside his comrades, Idomenius was able to survive the battle - and the firing of Installation 08 - by hiding inside the keyship. The group of loyalists would fall under the command of the Prelate Dhas Bhasvod.
Second Ark Conflict
By late-2559, Idomenius continued to serve in the loyalist remnant on the Ark. Following the arrival of the Lich Pegoras and its cargo of the Keepers of the One Freedom, the loyalist forces and Keepers forged an alliance to fight off the Banished and UNSC forces of UNSC Spirit of Fire in an attempt to fire the Halo Array. While the Keepers loaded their cargo into the loyalist Phantoms to head for the installation's Cartographer, Idomenius was ordered to resume the loyalist fight against the Banished in an attempt to recover the Menachite Forerunner crystal stolen by them months prior.
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