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. 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.