From Halopedia, the Halo wiki
During the Battle for Zeta Halo, on January 31, 2560, Chieftain Tremonius made a name for himself by leading a successful assault that wiped out a major UNSC survivor encampment at the wreckage of the UNSC Mortal Reverie. To commemorate his accomplishment, the War Chief of the Banished, Escharum, decreed that the first of many planned Banished strongholds on Installation 07 would be built at the site of Tremonius's victory, and would be named Outpost Tremonius in his honor so that the other the Banished would be inspired by his deeds.
On around May 28, Tremonius was in the House of Reckoning when the Banished's leadership received word that Spartan-II Master Chief Petty Officer John-117, who up to that point had been presumed dead, had destroyed the Ghost of Gbraakon. Infuriated and alarmed by the Master Chief's return, Tremonius began to sharply criticize Escharum's plans, going so far as to disrespect Atriox. This led Blademaster Jega 'Rdomnai to forcibly restrain and threaten the Jiralhanae. Escharum assured the bitter Tremonius that the Spartan's reappearance would provide the Banished with a much-needed challenge, and ordered his underlings not to interfere with the Spartan's activities for the time being.
Not long after this meeting, the Master Chief activated a Banished lift within the depths of Zeta Halo while searching for a way to the surface, but Tremonius was waiting and descended in the lift alongside two Kig-Yar Raiders. Tremonius announced that Escharum's orders were that the Master Chief should be brought before him; however, Escharum did not specify in how many pieces. Using a jetpack, Tremonius engaged the Spartan and the Weapon, but he and the raiders were outmatched and killed by the Master Chief.
After ascending the lift, which emerged within Outpost Tremonius, the Master Chief encountered a hologram of Escharum, who taunted him and dismissed the late Tremonius as one of the Banished's least remarkable warriors. As the Master Chief engaged the Banished forces holding the outpost, a Jiralhanae announced Tremonius' death over the loudspeaker and stated that whoever killed the Spartan would take Tremonius' place. However, the Master Chief cleared out the Banished and recovered the area for the UNSC's use for the first time since the Mortal Reverie had fallen to Tremonius and his forces.
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