Osiris was an old Warlock who was exiled from The City. He had knowledge about the inner working of the Hive, as he knew about the Shrine of Oryx. He was also said to have "come too close" to understanding the Vex.
After his exile, Osiris then started a cult, based on Mercury. It is unknown what happened to Osiris currently.
- Before the release of the game, it was thought that Osiris was one of several factions in The City.
- There are two known members of the Osiris cult who still live, Brother Vance and Sister Faora