User blog comment:ShawnCognitionCP/Your worst fear (Mini open collaboration, in a sense)/@comment-5321651-20150122045450

Sleep paralysis.

As you all may or may not know when you're dreaming your entire body essentially just shuts down; which is why when you're moving around in your dream, you're not moving in your bed (let's not go into somnambulism). Sleep paralysis is when you wake up, but your brain still thinks it's a dream. This causes you to be frozen still while seeing things such as people or shadows in your room. Most sufferers of sleep paralysis claim they see figures walking toward their beds, while they cannot move.... Terrifying. It's usually caused by sleep deprivation, so it's obviously a pretty likely occurrence for most of the users on this Wiki... Including myself.

Severe cases of sleep paralysis can be utterly terrifying.