Also along the lines of Ouija boards, my maternal great-grandmother was very into the occult. This would have been in the early 1900's. She would hold sťances, try to communicate with people in the afterlife, etc. I don't think she actually was a devil worshipper, but she really tried to look for "dark stuff".
My grandmother told my Mom that one afternoon, she went up into the attic of the house to do her thing. And came back down white as a sheet. Then she purged the house of everything she was using in her attempts and never did anything ever again. Apparently, something very, very dark and sinister decided to finally join her. She never said if it was Satan, but my grandmother thought it was.