Master Chief Petty Officer John-117

Master Chief Petty Officer John-117 is the player character for Halo CE. He was one of the few survivors of the SPARTAN-II project. Accompanying the Master Chief is the Pillar of Autumns feminine artificial intelligence construct, Cortana, who resides in a neural implant connected to his battle armor, codenamed MJOLNIR Mark V. The Pillar of Autumns captain, Jacob Keyes, is also a major character. Playing a mainly antagonistic role in the game's events is 343 Guilty Spark, an eccentric artificial intelligence responsible for monitoring and maintaining Halo's systems