[arx1422]

Every few years I get stuck for a few moments in the state between sleep and waking up. Always manifested the same way. In the middle of a dream environment a gateway with a totally alien, totally inexplicable intelligence would appear. I'd be paralyzed by it for a few seconds. As I got older a realized the terrifying alien world/intelligence was waking consciousness intruding into the dream state. Always interesting after I wake but true Lovecraftian horror as it happens.

[aalleavitch]

This is called sleep paralysis. It’s surprisingly common, and the source of a lot of folklore and ghost stories. I get it often: https://en.m.wikipedia.org/wiki/Sleep_paralysis