Intro. Master Chief, also known as john, is the protagonist throughout the Halo video game franchise. He, along with his AI companion, Cortana, have appeared in each of Halo's mainline games. Their main mission throughout the series is to defend humanity and Earth against aliens who want to use the Halo super weapon to wipe out all life in the galaxy.
In Halo: Combat Evolved, Halo 2, and Halo 3, their main antagonists were the Covenant, a theocratic alliance of alien races on a quest to activate a "Sacred Ring" that will annihilate all living things in the galaxy and send them on their "Great Journey," and the Flood, an ancient parasitic alien life form that reproduce and grow by consuming sentient lifeforms of sufficient biomass and cognitive capability. Other antagonists post-Halo 3 include the Prometheans, the Created, and the Banished.
The character is voiced by Steve Downes,[1][2] a former Chicago disc jockey. who based Chief's personality on Bungie's description of the character