I used to have occasional sleep paralysis, starting very young. I remember seeing shadows and hearing noises, then having them quickly gain resolution until I was actually hearing whispering and walking, and seeing something between a traditional western demon and an oni mask. Years later, before I learned not to sleep on my back but after I had a more materialist outlook, I would notice the process of forming images and usually be able to mentally halt the pareidolia.

I can easily believe that a more powerful such process would leave the formative steps imperceptible, especially to someone who had no experience.