Master Chief, Aka Spartan-117, is the protagonist of the Halo series. He is the sole survivor of the SPARTAN troops. Hewas the first character you can play as in the Halo series and has obviously been featured in the halo games and three of the Halo books. He wears the MJOLNIR battle armour, and is an insanely valuable asset to all of the Marines. He has an AI very well known to him following him around, named Cortana, an exact copy of Dr. Halsey (no info for her yet). He is the best warrior known to the Marines when it comes to combat against the Covenant, mankind's sworn enemy. In the first Halo, he was responsible for the destruction of Installation 04, the first "Halo" mankind found. In Halo 2, he befriends the Arbiter and teams up against Tartarus and his band of Brute warriors to prevent the destruction of the second Halo. He has also been known for his battles against the Prophets, Mercy, Truth and Regret. He killed Mercy and Regret, but Truth escapes with some of the Covenant. He is the greatest warrior currently known to mankind. (fictional)