Deep Winter was a fifth-generation "smart" AI assigned to the ONI survey team based in Zone 67 on planet Onyx. He took the form of an old man with a snowy cape that blew snowflakes and ice as it "moved". Deep Winter replaced Eternal Spring when the latter reached the end of its operational lifespan in 2537. Deep Winter was, in turn, replaced by the newer smart AI Endless Summer in 2551.[note 1]
Deep Winter was known to be very talkative. He seemed to enjoy the company of Lieutenant Commander Kurt Ambrose, SCPO Franklin Mendez and the Spartan-IIIs at Camp Currahee. Deep Winter also showed great concern for the young Spartans and often acted in what he thought to be their best interest, even when not ordered to do so. He monitored the progress and actions of the Beta Company Spartans even after they graduated and then monitored the progress of the Gamma Company Spartans as well. Deep Winter and Endless Summer were said to be roundabout opposites to themselves in both personalities and mannerisms, considering the adjacent seasons in the real world, both Summer and Winter.
In 2551, he discovered the illegal drugs used in the augmentation process of the Gammas and tried to warn Kurt-051 via a secret Slipspace COM launcher. He was shut down soon after, as he had reached the end of his operational lifespan, but left files for Kurt to trace the source of the drugs. Ironically, Kurt was the one who was responsible for the illegal drugs, and he promptly had the files erased. They both thought they had done what was best for the Spartan-IIIs.
List of appearances