Demons. Fear or not? - generally speaking, not.
I'll watch all manner of films that are about demonic possession. The Exorcist (1973) and Hereditary (2018) are very good films.
But I'd never play a Ouija board or anything like that. My reasoning is that I don't know, 100% for sure, if demons exist or not. There's no evidence for their existence, I hope they don't exist, but I don't know for sure. In light of this, I think it's pretty sensible to steer clear of Ouija boards and other efforts to contact spirits.