From Halopedia, the Halo wiki
After five years of near-constant conflict, Sundered Legion forces were defeated by the United Nations Space Command at the Siege of Athea on Meridian. Leaders of the Sundered Legion were placed on trial in the courts of the Unified Earth Government, though the rest of the faction's members were offered amnesty by the UNSC.
By 2548, the Sundered Legion faded into the past. Rumors persisted at that time that a bunker underneath the town of Brume-sur-Mer officially built at the start of the Human-Covenant War, had actually belonged to the Sundered Legion. During the Battle of Meridian that same year, Saskia Nazari, Victor Gallardo, Dorian Nguyen, Evelyn Rousseau and Spartan-III Owen-B096 located an abandoned and long-forgotten Sundered Legion hanger near Brume-sur-Mer. The hanger contained a Prowler that the Legion had presumably stolen from ONI during the Insurrection and which was still functional. The presumed great-grandson of one of the Legion, Dorian's DNA allowed him to access the ship's systems and fly the survivors from Brume-sur-Mer off of Meridian.
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