I've been working in a haunted insane asylum. The place has been under construction for the past 3-4 years. It's a new 1 million square foot building on the insane asylum grounds. I don't think I believe in ghosts, but now that construction has come to an end, weird stuff has been happening that I cannot explain. Locked doors that require a key or RFID badge to unlock, unlocking and opening by themselves, doors with automatic hydraulic door closers holding themselves open, lights turning on and off by themselves, footsteps, disembodied voices, strange sounds, strange shadows/shapes showing up on CCTV feeds, and inanimate objects moving by themselves. All my coworkers have had something happen to them there they can't explain. All the activity started up about 2-3 months ago once construction finished.
Though I know for a fact there were forms of it mixed with actual Aryan Zoroastrian mythology (Manichaeism) and other more debased forms, particularly the Antinomian sects of Syria.