Ten years ago, my flatmates and I had an ongoing conversation about doing a horror production of Hamlet where the Ghost really was a devil. In Act Two, Hamlet wonders if the Ghost is an evil spirit preying on his depression:
The spirit that I have seen
May be a devil: and the devil hath power
To assume a pleasing shape: yea, and perhaps
Out of my weakness and my melancholy,
As he is very potent with such spirits,
Abuses me to damn me.
and we thought it could be fun to see what would happen if he was right to wonder that.