Sif

Sif was a UNSC Shipping Operations A.I. on the Tiara Space Station, in orbit above Harvest. Near the center of the Tiara was a room which housed her data center that contained the processor clusters and storage arrays that served as her core logic.

Chosen Avatar
Her chosen avatar is in the form of a woman with an ankle-length sleeveless gown and long golden hair. It is also mentioned that she has a red poncho that she drapes over her shoulders. She has the appearance of Nordic royalty. She chose this avatar because many of Harvest's settlers were from Earth's American heartland, who could trace their ancestry back to Scandinavia. This may also be result of the flash cloning process, as Sif was cloned from a human implied to be of European nationality. Her human source may have also affected Sif's choice of avatar hair color, as her human counterpart loved her own blond hair.

Role
She is in charge of Harvest's shipping operations which included the balancing of the Tiara, the transporting of human and shipping traffic up and down the space elevator, and control of the passenger and cargo transport in and out of the Tiara, as well as shipping manifests and keeping cargo on schedule. The A.I. Mack flirts with Sif often, usually to her annoyance and frustration.

As the Tiara was invaded by Brutes and Grunts from the Rapid Conversion, Sif was incapacitated by Loki, who used a military-grade virus to delete her restraint algorithms and operational codes in an attempt to prevent her from falling into Covenant hands. Her core logic was later partially restored by the Huragok Lighter Than Some, although in the absence of emotional self-control programs, she came back online rampant. Despite her rampant and severely weakened state, she rejoined the fight to rescue the citizens of Harvest. With Lighter than Some continuing to repair her systems on the fly, Sif assisted Loki in rebalancing the number 7 strand after a Brute attack threatened to destroy it. Following the evacuation, when Loki decided to destroy her, she agreed and helped him convince Mack to allow it. She told Loki to relay to Mack that she loved him. Soon after, Loki shot a Mass Driver round into her data center, destroying her and the Tiara. She attempted to go through the many emotions that rampancy afforded her; however, she found them all to be untrue to her. She ultimately died content, feeling that she had lived a fuller life than her makers had ever thought possible.

Trivia

 * Sif is the wife of Thor in Norse mythology.
 * In Norse mythology, Sif and Loki factually did not correlate with one another often. In the Myth, The Treasures of the Gods, Loki managed to get into Sif's locked bedroom and hacked off all of her golden hair as an unfeasible prank. Thor eventually caught him and made him retrieve fake hair from the Dwarves. Just like in Halo: Contact Harvest, Sif is constantly irritated with Mack (or rather Loki's) presence, comparable to their Norse mythology predecessors.
 * Sif was one of the few AI that went rampant, ultimately ending in her destruction and demise on Harvest.
 * In the Contact Harvest audio book Jen Taylor, the voice of Cortana, takes over the narration when Sif is the focus of events.
 * Her human memory, as it were, is the feeling of the gentle tug of a hair brush through her hair.