I've been working in a haunted insane asylum. The place has been under construction for the past 3-4 years. It's a new 1 million square foot building on the insane asylum grounds. I don't think I believe in ghosts, but now that construction has come to an end, weird stuff has been happening that I cannot explain. Locked doors that require a key or RFID badge to unlock, unlocking and opening by themselves, doors with automatic hydraulic door closers holding themselves open, lights turning on and off by themselves, footsteps, disembodied voices, strange sounds, strange shadows/shapes showing up on CCTV feeds, and inanimate objects moving by themselves. All my coworkers have had something happen to them there they can't explain. All the activity started up about 2-3 months ago once construction finished.
Demons do not have free will, because they have knowledge of eternity's past (or rather near to eternity's past as they are created beings), and also knowledge of eternity's future (or near to it, but they don't know the time of Christ's return. Other than that all of them know basically everything). It's impossible to have free will when you know both what *has* happened and what *will* happen. Their only chance to see a diverging existence from their current course is by interacting with humans who do have free will, because we do not know the future. Only the past and some of the present.