Rebecca

"We're at war, Commander. Reach has fallen. Our backs are against the wall. Extreme measures are necessary to ensure our survival."

- Rebecca

Rebecca is a UNSC "smart" AI and the shipboard artificial intelligence of the, an ONI prowler.

Mission to Soell
In October 2552, Rebecca was commissioned by the Office of Naval Intelligence to monitor the Red Horse during a top-secret mission around the ruins of Installation 04. She replaced the Red Horse's former shipboard AI, Chauncey, much to the dismay of the personnel aboard Red Horse, who preferred Chauncey's openness over Rebecca's secretive and cold demeanor.

As a Pelican full of marines was sent to investigate the prisoner transport Mona Lisa, Rebecca refused to give away any information on the ship's nature, even to Commander Tobias Foucault, saying "We have our orders, Commander." After communications with the Marines aboard the Mona Lisa had been cut off, Rebecca insisted the Red Horse destroy the ship, again deferring to their orders. Foucault was hesitant to do so, having grown increasingly frustrated about Rebecca's secrecy, but eventually gave the order after Rebecca showed him what had compromised the Mona Lisa: an alien parasite known as the Flood.

Appearance
She is one of two known AIs to have an avatar with two different, interchangeable appearances. Her first appearance is described as "half-Athena, half-Ares" with a feathered Greek headdress and ancient armor. She could change her appearance to a flabby, middle-aged Mediterranean woman in a flower dress, which she apparently did in order to make people around her feel more relaxed.

Commander Foucault often insisted that Rebecca use her warrior avatar, viewing it as disrespectful of her to appear on the bridge as a "dumpy Italian woman" due to his rigorous sense of decorum. However, this was also because the other appearance made him underestimate her.

Trivia
Though she alternates between two appearances in the Halo: Evolutions story, she is only seen using her "warrior" avatar in the motion comic adaptation of The Mona Lisa, likely to avoid confusion.

List of appearances

 * Halo: Evolutions - Essential Tales of the Halo Universe
 * The Mona Lisa