Beat DD, the protagonist decides to keep the damned one. Beat BD, the protagonist releases the damned one from imprisonment. Beat Div2: ED, and the protagonist releases the damned one's lover from the prison of... death. Beat Div2's expansion and you kill off his lover for good. While it's not stated, you can easily assume that at the end of DKS, Damien is utterly pissed and is totally going to unleash hell upon the world.