Cortana

Bio
She is the only UNSC AI generated from Halsey's living tissue. She is John 117's long time AI companion until Halo 4, where she sacrifices herself so Chief can survive. She was found in Halo 5, still alive, but corrupted with divine control over the Promethean forces. She had conquered all known territory. She had attempted to get Master Chief to join her, but he declined due to how wrong her cause was. They are now reluctant enemies.