Cassie was an AI who was once Swift's sister. After her death, the AI that integrated with him used his memories to gain the traits of Cassie, so she was "resurected" in AI form.
Cassie was in the spartan III academy with swift. While there, she built up a romantic relationship with Ocelot. As the years went by, she wanted more and more answers. she eventually hacked ONI's sensitive files, but was caught and sent away for a while. When she returned, she no longer acknowledged Ocelot as a love interest, leaving him heartbroken. the team was later assaigned to an unknown planet, where Cassie fell in love with a native. One night, they were attacked by the covenant, and the native was killed. The next day she went offalone to confront the covenant and did not return. She is presumed to KIA, though she could MIA. She was later ressurected as an AI and assisted Swift in many battles.
Early on, she is kind and friendly, and as Ocelot said, "liked by everybody." she was known to help out with the warthogs when she had spare time. she also took the time to say by to her younger brother.
- she is one of the few characters/the only character in the series to have a blue visor.