When I was growing up, Ouija Boards were a Big Thing. They consisted of a board with letters around the edge, and a planchette, a wheeled pointer that would be used to point at letters to form words and sentences. The 'operator's eyes are closed.
And, of course, the messages came from...somewhere else...and were transmitted through the person whose hands lay on the planchette.
A variation on this exercise is automatic writing, in which a pen is mounted to the planchette, and is used to actually write the words. (A vivid description of automatic writing is given in Nevil Shute's novel No Highway; Shute is the bloke who wrote A Town Like Alice, serialized on PBS a number of years back.)
Seeing this in practice is unnerving, because while often the 'messages' are gibberish, sometimes they're not. They can be bland, like "Hello" or "How is the weather?", or simple, and slightly incongruous statements such as "There is a table".
Occasionally they seem friendly.
And there are a significant number of communications that are evil, filled with hate and fear and threat. Makes the hair on the nape of my neck stand up, writing about them. I won;'t quote the ones I have seen.
It's easy to dismiss the Quija Board / automatic writing phenomenon as an expression of the operaor's subconscious - i's what his benighed, blindfolded person would wan to say.
That's a simple, rational explanation. I believe it's quite wrong. First, in cases I've seen there's been a lack of internal consistency in the 'personality' and knowledge base of the operator and what was written. Phrasing was different, and there were things written that the operator should not have known.
Second, visual observation of the planchette's movement indicated some kind of external control. It was jerky, but the operator's hands were relaxed.
Something is out there...but what?
I don't think it's your Dear Departed Aunt Mildred. If you look at near-death experiences, and at the Bible, you find no indication that the 'departed' would have any trouble contacting us if they needed to do so. We are their 'shadow world'. A clumsy board 'game' would be laughable to them.
So, who? Given the number of malign contacts that come up, I think that when we play around with this stuff, we kick a hole in the 'hedge of protection' God has put around us...and give access to something unspeakably bad.
The existence of demons has been a given in almost every culture on this planet - including Western Christianity. Some would now scoff, thinking that, well, we can go to the moon, and we're too grown up to believe in demons.
We can no longer go to the moon. That knowledge and experience base has been lost.
And the demons aren't scoffing. They're waiting.
Don't play around with this stuff.