Kyrin 'Forus (formerly Forusee) was the leader of the Grey Rebellion and instigator of the Y'deio Uprising. On Sanghelios, he served as a Tactics Master training young Sangheili in the art of war. Later, when he joined the Covenant Navy, he served devoutly until he was promoted to the rank of Fleet Master and given command of the 2nd Fleet of Undying Justice, a fringe-space peacekeeping fleet which later became known as the Grey Fleet.