Déjà

Déjà is a "dumb" AI who trained the Spartans in their first stages of training at the CASTLE Base and Reach Naval Academy facilities on Reach. She taught them terms such as Oly Oly Oxen Free. Her educational lessons were part of the Spartan's training program, meant to increase their strategic thinking. She also educated them in history, math, and other things most people are taught. One of her first lessons she taught the Spartan-IIs was the famous Battle of Thermopylae, where 300 Spartans made a stand against a quarter of a million Persians

Her counterpart, Chief Petty Officer Mendez, gave the Spartans rigorous physical training to make them into soldiers. This, along with Dr. Catherine Halsey's physical augmentations and MJOLNIR armor, made the Spartans intelligent, strong, and fast.

She is presently dead for Dr. Halsey used the AI self destruct program to protect her Spartans.