[He doesn't want to explain this. He doesn't want to remember the Meta, the creature that had burned Maine out and destroyed him. But he owes it to him doesn't he?]

Sigma. Your AI. He... the AIs were just fragments. Parts that had been broken off the Alpha. Through torture. Sigma thought he could become more than that if he got hold of the other fragments. And he used you to do it. Took over bit by bit until I don't think you were in there, or you'd been buried. He used you to do terrible things.