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.