It seems a common topic to inspire horror among humans. It is virtually unheard of among dwarves or goblins, and among all three races of elves it is known under a different name and has nothing to do with demons. In fact, for elves, it is often used as part of healing magic. This is not to say it doesn’t exist, or isn’t possible, but it doesn’t exist to the extent that many seem to believe. Why would it? What do mortals think we gain by possession?
Only the strongest of named demons can even do it, and we have no reason to. Lesser demons would likely do it if they could, just for the mischief they could wreak, but it does not net us souls. It is draining to us, and we are severely constrained in a mortal shell.
Instead, think on this: if I wanted to trick you into thinking I’m another human, I have both the power of illusion and the ability to shape-change. I hardly need to “wear” another person to take you in.
That should be far more frightening, that I could be anyone, and you can’t see through it.