You know how people say 'I like to see the good in people'? I want to find the devil in everyone. I want to see what someone's dirty little secrets are; I want to witness someone being totally selfish and cruel; most of all, I want to recognise evil when I see it, as it's more healthy to know what to avoid being rather than try be something no one can be.
Everyone has a bit of the devil in them; if you read Paradise Lost without a Christian mindset, a whole new image takes form. The Devil corrupted Eve, and from then on all life, all beings, every inch of Eden and the world below it was tainted with the Devil's lure. God couldn't avoid it, and the Devil found the weakness in God's 'great creation', corrupted it, and then just sat their watching the world burn. He didn't gain anything from it, apart from pissing off God, and having a good jaunt down to the Tree of Knowledge for the afternoon.
All in a day's work. Impressive guy, the Devil.
P.S. I'm not Satanic, or a Satan worshiper or something. It's all in aid of research. Thanatos is going to be the best damn devil you ever did see / read.