Halo is a science fiction video game series created by Bungie Studios and published by Microsoft Game Studios. The series centers on the Master Chief, a cybernetically-enhanced human super-soldier equipped with technologically-advanced battle armor, and his artificial intelligence (AI) companion, Cortana, as the humans of a futuristic universe battle the Covenant, a theocratic alliance of alien races. In this science fiction setting, the term "Halo" refers to Halo megastructures, large orbital constructions.