I think that the real Sid is trapped inside his own body and the demonic Sid is someone else (probably one of his demon voices) using his body as their vessel/form. Remember he has little to no control over the voices so they could just as easily push him into the space he’s at now with all his eye friends. The satan part I’m guessing is Satan trying to use his temptations and weaknesses to make him agree to something (which he refused to). Remember the original plan was to destroy Satan (or something like that). I’m also guessing that the the demonic guy took over whenever he was using the officer friend (forgot his name).

I'm confused with the whole Satan thing.... Is Satan the reason why Sid betrayed Cain in the first place, or Sid just did it on his own? Also what the heck where they talking about, I was lost thru out all od that part with Satan talking. lol