Sleep paralysis
Sleep paralysis is a condition where a person is suddenly awoken from REM sleep to semi-consciousness, but their body is paralyzed to prevent acting out dreams. Shadow people and Old Hag syndrome are very commonly reported by victims. Because of the sudden awakening, lack of control, and presence of seemingly malicious entities, sleep paralysis tends to be a frightening experience for any who aren't prepared for it.
An easy way to get out of sleep paralysis is focusing on moving one part of the body to snap out of it.
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