 Halo is a military science fiction first @-@ person shooter video game franchise created by Bungie and now managed and developed by 343 Industries , a subsidiary of Microsoft Studios . The series centers on an interstellar war between humanity and a theocratic alliance of aliens known as the Covenant . The Covenant , led by their religious leaders called the Prophets , worship an ancient civilization known as the Forerunners , who perished in combat with the parasitic Flood . The central focus of the franchise builds off the experiences of Master Chief John @-@ 117 , one of a group of supersoldiers codenamed Spartans , and his artificial intelligence ( AI ) companion , Cortana . Other characters , such as Noble Six from Halo : Reach , are also introduced in the series . The term " Halo " refers to the Halo rings : large , habitable superweapons that were created to destroy the parasitic Flood . They are similar to the Orbitals in Iain M. Banks ' Culture novels , and to author Larry Niven 's Ringworld concept . 
