Hardcore proof? could be difficult to find.
All i have is the way certain situations make you feel.
About 16 yrs ago i used to inspect security systems for home inspectors and prospective house buyers. I go into this house and started doing my thing, i go into the last room and notice a satanic bible a ouija board and other occult things. I start feeling like im being watched, so i leave the room only to be met by a very pretty woman in the hallway. She says hi and she starts talking and being rather direct, eventually inviting me out for a drink. I say sure. I don't even know why i agreed, because i had a creepy feeling talking to that chick (kind of felt in a trance)
So i leave my report on the kitchen island, and say later to the inspector (who gives me a wtf look). I start walking towards my truck and i notice the woman looking at me through the window, she is just staring at me. i get in my truck and notice she is still staring at me.
Later that day i see the inspector again. I tell him that the chick (who looked a bit like isla fisher) invited me out for drinks. He then tells me he had no idea i liked ugly women, because the woman he saw in that house was not the one i just described. He said maybe she left and someone else came in the house (when he was in the attic). But that was impossible, because there was no way someone could have went in the house in that time frame. I wasn't drunk, hungover or anything. I'm 100% sure had spoken to a hot redhead earlier that day.
I still can't explain it. And i never went on that date. Could it have been a demon? who knows
I have a few other stories that my aunt who used to "play" a ton with ouija boards told me.