I don’t know of a single soul who has had sex with a demon. Now, that being said, I know a few who have called their exes the spawns of Satan, but I’m pretty sure that was for effect.
I may regret asking this, but how would anyone know they had sex with a demon? Would that not be apparent pre-encounter? Actually, don’t worry about it. I don’t think I want to know. No offense.
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Satanists do this sort of thing. A being appears out of nowhere then gone when deed is done. Demons can inhabit animals such as dogs, and dare I say cats etc. then transform , shape shift into another form, such as human appearance. The stuff you see in movies and TV sometimes are reconstructions of what they have experienced. Many of us know that the movie and music industry is full of these types of folks.