The Halo 3 Campaign
Halo 3 is the conclusion to the Halo Trilogy. The main character Master Cheif returned to Planet Earth to stop the Prophet of Truth and the rest of the Covenant armada from reaching the Ark, the controller to fire all remaining Halo rings throughout the universe. If he succeeds, all living being's in the galaxy will be destroyed. The plan was for Master Cheif to beat the Covenant to their plan. Along the way, Master Cheif and his newly found elite allies (who used to be with the Covenant but left after being told falsely by the prophets) and the Arbiter (the leader of the elites) would take on the Covenant with all they had. But along the way, the Flood (the beings from halo itself) try to interrupt both Master Cheif's and The Prophet's plans. This story goes well in depth to wrap up the trilogy to this amazing game series.
Master Chief
Master Chief is the last remaining Spartan from the Spartan II project. He is well known for his combat abilities and his heroic leadership.
The Arbiter
Disgraced by the Covenant this elite was made the servant of the Prophets. But after he learned about the Prophets wrongful plan he left along with his elite brothers.
The Prophet of Truth
The Prophet of Truth was the leader of the Covenant who planned to send the Covenant into the Great Journey by firing all the Halo Rings. What he didn't know was that his plan would kill every living being in the universe.
Cortana
Cortana is the computer AI that has helped Master Cheif throughout his UNSC life. She has been programed to store data, intercept transmission, and hack computer files.
Miranda Keyes
Miranda Keyes is a Commander in the UNSC. She is well known in battle tatics and strategies.
Sgt. Major Avery Johnson
Sgt. Major Johnson is one of the toughest marines in the UNSC. He was one of Master Chief's best friend and ally.
Lord Hood
Lord Hood is the main General of the UNSC. He wants to stay to protect Earth instead of chasing after the Prophet.
343 Guilty Spark
Monitor of Installation 04 the first Halo ring who left after the Master Chief destroyed it. He then joined with the heretic group against the Covenant and then left with the Arbiter and the elites.
Shipmaster
One of the Arbiter's most trusted allies, Shipmaster commands the cruiser Shadow of Intent. He planned to glass the entire Earth, but the Arbiter talked him out of it.
Gravemind
The Advanced form of the Flood, he can think for himself, talk, and control all the Flood as their leader.