I think I like your demons better. In Thedas, demons will possess mages like me so that they can get a foothold into the mortal realm. They kill and torture humans for fun or to feed off their emotions and things. A mage possessed by a demon becomes a horrible abomination, and most of the time there's nothing human left in them at all.

They're a bit of a worry for all mages, and the Chantry uses it as justification to lock us up and kill us if they think we're possessed, among other things.