Halo is a military science fiction media franchise created by Bungie. The franchise is currently managed and developed by 343 Industries, and owned and published by Xbox Game Studios. The central focus of the franchise builds on the experiences of Master Chief John-117, one of a group of supersoldiers code-named Spartans, and his artificial intelligence (AI) companion, Cortana. The original trilogy centers on an interstellar war between humanity and an 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 while defeating the parasitic Flood. The eponymous Halo Array are a group of immense, habitable, ring-shaped superweapons that were created by the Forerunners to destroy the Flood, but which the Covenant mistake for religious artifacts that, if activated, would transport them on a Great Journey to meet the Forerunners. They are similar to the Orbitals in Iain M. Banks' Culture novels, and to a lesser degree to author Larry Niven's Ringworld concept. The games in the series are critically acclaimed, with the original considered the Xbox's 'killer app'. This led to the term 'Halo killer' being used to describe console games that aspire, or are considered, to be better than Halo. Fueled by the success of Halo: Combat Evolved, and by marketing campaigns from publisher Microsoft, its sequels went on to record-breaking sales. By 2015, the games had sold over 65 million copies worldwide, with the games alone grossing almost $3. 4 billion.