From Halopedia, the Halo wiki
During the Forerunner-Flood war, Zehar VI was one of a number of ice worlds alongside Kamchatka and Strilun IV to play host to the interests of the Lifeworkers. These worlds were used to house extreme rehabilitation complexes built within the planet's glacial layers.
In the later years of the Human-Covenant War, Zehar VI was occupied by the UNSC. The humans built and maintained a network of secret holdouts on the planet for use as fallback positions for key personnel and assets, though they later took an interest in what lay under the planet's surface and in peculiar findings on the planet's two moons.
Originally, the planet was stated as being part of the "Zezar" system in a Canon Fodder post, which was also supported by displays found on the map during the Season 6 flighting of Halo: The Master Chief Collection. However, those same displays were changed to say "Zehar VI" by the time the season was released and Waterfall was officially added to the game. Despite this, "Zezar VI" could still be seen in shadow behind the "Zehar VI" text. As of Season 7, the screens identify the planet as Zehar VI, with the shadowed text being fixed to reflect this new name as well. The Zehar name was later referenced in the Halo Encyclopedia (2022 edition).
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