Cortana (Novum Acies)

"This Galaxy is vast; its wonders and beauty are almost unfathomable. But the galaxy also hides dark secrets, some of which have lain dormant since the beginning of time itself. There is a danger in secrets, both in seeking and in knowing. Some things are meant to be hidden from view. Some mysteries defy understanding, and sometimes even the things we think we know are untrue. Some secrets should remain untouched."

- Cortana

Cortana ( CTN 0452-9) was a affiliated with the. Entering service on November 7, 2549, Cortana was created from the brain of the brilliant mastermind behind the,. Originally created for the high-risk, Cortana was to have the best mind currently available in the UNSC's staff for the intensive infiltration and decoding properties she had to have in the op. Due to that, the branch agreed and had Dr. Halsey's brain flash-cloned several times, even with the high probability that the cloned brains wouldn't be stable for enough time to create the AI. However, miraculously, two brains stayed intact long enough for two "smart" AIs to be derived from each; Cortana and Kalmiya.

However, the brain from which Kalmiya was derived was a bit damaged, causing her to not have the same capabilities as Cortana. She found use as Dr. Halsey's personal AI, working more efficiently and closer to her than the other AI with Halsey,. Cortana was chosen for the still-to-be-planned-out Operation: RED FLAG. For a brief period of time from 2549 to 2551, Cortana served as the "smart" AI accompanying the cross-branch GAUNTLET Team, led by Tyler-A319, in order to test her effectiveness in the field and continuously improve her specialties. Cortana received critical-acclaim from the Spartans of the team as well as the staff, setting up her future. From 2551 to 2552, Cortana was repurposed to work with Dr. Halsey again as the final planning for RED FLAG was being done, and she and Kalmiya proved to be excellent partners in her work.

In 2552 on, Cortana was introduced to , also commonly known as the "Master Chief", with whom she was paired for RED FLAG, accompanied by the rest of the SPARTAN-IIs. The SPARTAN-IIs were also provided with the Gamma (or) finalized version of the, and would receive assistance from the completely-refit the , captained by Cpt. . They were almost about to embark on their mission when it was scrubbed due to Reach being attacked. After a quick stream of events, the Pillar of Autumn escaped Reach jumping to a random location in space via slipspace. That would change humanity's fate forever, as the jump caused the ship's crew to discover, also known as Alpha Halo. There, John-117 and Cortana encountered the parasitic and discovered the ancient existence of the long-extinct  race. A brief battle ensued, in which Cortana absorbed a vast amount of knowledge from the Halo's archives before it was destroyed by the Master Chief.