Id

About

Id was the result of the trauma Fei endured as a child. He is defined by emotions like hate, resentment, and anger, because that is all he has ever experienced. He wants to destroy everything and kill everyone, and doesn't really consider much beyond that. Fei's memories of Lacan and his other past lives are kept hidden by Id, who is stronger than the personality Fei wears most of the time during the game. He is also known as the Demon of Elru.

Though they are not Id, Fei has two other personas: The Unnamed, and the Coward (his original persona). The Coward has some control over Id, while the unnamed is below him.

(Source: Guardian Angels)