Alpha Tribe

Alpha Tribes are a larger grouping of Jiralhanae (Brutes), likely more than a Master-Pack, and seem to be the governing body of the Jiralhanae as a people. Before the Brutes' integration in the Covenant, probably no Alpha tribes were in existance on their governing body, resulting the leadership to be fragmented, explaining the Master Packs predominance during those times, which, ultimatelly, caused the civil wars that devestated Doisiac. The Alpha leadership was lured to Joyous Exultation under pretense of truce negotiations - actually a Sangheili ambush to eradicate the Jiralhanae leadership. The planet was devastated by a UNSC NOVA Bomb before the ambush could be sprung, and whether the Alpha's survived, or even arrived for that matter, is unknown.

Trivia

 * Many of the familiar Brutes from the Halo series, like Tartarus, Lepidus, and others, were most likely part of this tribe due to their high command positions.