When I was a kid, back in 57 or 58, I asked an elderly neighbor lady if she believed in ghosts. She said no, and I asked why she didnt. What she said has always stuck with me. Those people in heaven dont want to come back, and those people in hell cant come back. True, but ghosts could be some form of demonic manifestation. And it wouldn't be beyond demonic powers to impersonate the dead, whether during seances, as ghosts, or as poltergeists.
True enough. But they would be fakes. The ladly was talking, as was I, about real ghosts, the spirits of dead people.
I hadn't advanced far enough in my understanding of either theology or the occult to know about demons. The Devil, sure, but not his legions.