Loki

Loki was an Planetary Security Artificial Intelligence construct in service with the United Nations Space Command. It was stationed aboard the Phoenix-class Colony Ship, UNSC Skidbladnir . Loki was then taken over by the AI Mack. Loki and Mack had done this many times, to prevent rampancy caused by old age. Loki waited in Mack's processor for the time when he may be needed, and when he was he took over Mack. Loki is unlike any other AI because he can trade places with Mack and besides a few minor variations of the avatar they look the same. When Harvest was attacked Loki was the one who made the escape plan. He was also the one who destroyed the Tiara and killed Sif.

Trivia

Loki is named after the god of chaos in Norse Mythology. He was an adept shape-shifter and could change not only his form, but also his sex, possibly referencing the ability to switch between himself and Mack. In Norse Mythology, he usually plays the role of villain and trickster.