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Deja 2.png
Biographical information

Began service:

December 22, 2510[1]

Ended service:

August 30, 2552 (presumed)


Female programming[2]


Greek goddess[2][3]



Political and military information



  • Teacher for the Spartan-II candidates[2][3][1]
  • Assistant to Dr. Catherine Halsey[3][1]

Service number:

DJA 0552-1[1]


Déjà (AI Serial Number: DJA 0552-1) was a custom "dumb" artificial intelligence who acted as a personnal assistant to Dr. Catherine Halsey and as one of the primary instructors for the candidates of the SPARTAN-II program.[2][1]

Operational history[edit]

Teacher of Spartans[edit]

Déjà served as an educational AI for the SPARTAN-II training program, instructing the SPARTAN-II candidates in their first stages of training at Reach Naval Academy and other facilities on Reach. Her counterpart, Chief Petty Officer Franklin Mendez, gave the Spartans rigorous physical training. This, along with Doctor Catherine Halsey's physical augmentations and eventually MJOLNIR armor, made the Spartans more intelligent, stronger, and faster than their non-augmented counterparts.[5]

Déjà's lessons were the part of the Spartans' training program meant to teach them to employ strategic thinking. She also educated them in history, mathematics, and presumably other fields. In one of her first lessons, she taught the Spartan-IIs about the famous Battle of Thermopylae, where 300 Spartans made a stand against a quarter of a million Persians.[6] Another lesson was about seven wolves taking down a moose, by working as a team. This served as one of the Spartans' earliest lessons about the importance of teamwork; that a wolf alone would be a far less effective hunter than if it were accompanied by its pack.[7] During one of Mendez's training missions, she helped the Spartan trainees when John-117 called her instead of Mendez. Using a mail link, he linked her to an Albatross dropship to request she show him how to fly it to get the Spartans home. While she couldn't do that, she had him activate the autopilot, allowing her to take control of the craft and fly the Spartans home herself remotely.[8]

Halsey's aide[edit]

Déjà often acted as a sounding board for Dr. Halsey, discussing how the Spartan-II Program should be run. For example, the night the program officially began she advised Halsey on how to address the children. They also would discuss the treatment of the individual Spartans, as well as the ethics of their situation. As a "dumb" AI, Déjà would tend to take the less emotional, more clinical side of these discussions: One example is when she asked Doctor Halsey if she was giving Soren-066 the choice to proceed in the program in order to alleviate her own conscience.[9]

On March 31, 2526, Doctor Halsey sought Déjà's help in figuring out where a Covenant supply depot was based off a recovered Covenant kelguid and the arrival of a supply convoy to Etalan five days after the decimation of the Fleet of Inexorable Obedience's logistics flotilla. Déjà suggested that the Covenant had instantaneous interstellar communication, allowing for the location they were looking for to be a planet five days slipspace travel from Etalan of which there was one. During this conversation, Déjà glitched, experiencing several erratic pauses. By this point, Doctor Halsey had traced the source to a sophisticated data miner slipped into her lab's systems by Hector Nyeto or one of his operatives. She didn't bother to correct it because Nyeto had already gotten access to her most closely guarded data and Doctor Halsey didn't want Nyeto to know that she was onto him. Doctor Halsey realized that Déjà's explanation was the most likely answer for the problem. Déjà then took her leave as Colonel Marmon Crowther arrived to talk with Doctor Halsey.[10]


Her current fate is unknown. As a "dumb" AI, her lifespan is, in theory, indefinite. However, Déjà was last seen on Reach in 2552, residing inside CASTLE Base. It is unlikely that her server clusters survived the base's destruction during Operation: WHITE GLOVE.[1]

Personality and traits[edit]

Given that she was a "dumb" AI, Déjà tended to be rather stoic and rarely showed emotion. This was shown in her voice pattern, which tended to be very steady and smooth as silk.[11] Déjà's intelligence within her fields of expertise was equivalent to a human IQ of 240.[12]

When displaying her avatar, Déjà took on the appearance of a Greek goddess.[2][3] She was barefoot and wrapped in the toga, with motes of light dancing about her luminous hair. She could often be seen holding a clay tablet covered with binary cuneiform markings in her hand.[2]


  • Déjà's name means "already" in French.


List of appearances[edit]


  1. ^ a b c d e f Halo Encyclopedia (2022 edition), page 109
  2. ^ a b c d e f g h Halo: The Fall of Reach, chapter 3
  3. ^ a b c d e Halo: The Fall of Reach – The Animated Series
  4. ^ Halo: Fall of Reach - Boot Camp
  5. ^ Halo: The Fall of Reach
  6. ^ Halo: The Fall of Reach, page 47
  7. ^ Halo: The Fall of Reach, page 39
  8. ^ Halo: The Fall of Reach, chapter 5
  9. ^ Halo Evolutions - Essential Tales of the Halo Universe, Pariah
  10. ^ Halo: Silent Storm, chapter 22
  11. ^ Halo: The Fall of Reach, page 55
  12. ^ Dr. Halsey's personal journal, May 3, 2526