Here's the details, the game will support four-player co-op via both Live and System Link with up to two player per a television on split-screen. To access the game you go into the lobby and set the mode as Campaign and then invite your friends. Unfortunately, you won't be able to drop into an active co-op game.
The lead gamer plays as the EmCee, while player two gets to control the Arbiter and players three and four control "two brand new Elite characters." Hit the jump for their descriptions.
PLAYER 3 (Sangheili)
Name: N'tho 'Sraom
Affiliation: Fleet of Retribution/Special Warfare Group/Special Operations
History: N'tho 'Sraom is the youngest member of his Special Operations unit and is one of a growing number of human sympathizers amongst the Sangheili youth. He is a fairly typical young male adult Sangheili--he began compulsory military service at the end of adolescence, and remains unmarried with no close, non-familial relationships outside of his martial order. N'tho Sraom refused to stand idly by while the Prophets replaced Sangheili units with Jiralhanae packs, and now bears deep resentment toward those Sangheili politicians who landed his kind in their current predicament.
Although N'tho 'Sraom's romanticized nationalism is emblematic of all Sangheili, he has developed a healthy respect for humanity--not for their physical abilities or martial prowess, but for their audacity and resolve.
PLAYER 4 (Sangheili)
Name: Usze 'Taham
Affiliation: Fleet of Retribution/Special Warfare Group/Fleet Security
History: Although Usze 'Taham was born into a respected merchant family he was fathered by Toha 'Sumai--one of the preeminent swordfighters of this age. Usze graduated with honors from the top War College in the Iruiru region of Yermo, Sanghelios (a distinction he shares with Rtas 'Vadum). Shortly after receiving his first post within the Covenant Navy he was offered a place on the Prophets' Honor Guard but he declined citing "lack of practical experience". In truth, he had no desire to be part of a largely ceremonial unit, and at the end of his third combat tour, Usze 'Taham again refused the post--even though his superiors warned him such behavior could be misinterpreted as apostasy.
Since that time Usze has evaded countless punitive actions, at least two assassination attempts, and served with distinction for two additional tours before the Schism. Following the dissolution of the Covenant, he was approached by the Ascetics to become one of their liaisons within the Navy.