Parasomnia is a category of sleep disorders involving unusual behaviors, emotions, movements, or perceptions that occur while falling asleep, sleeping, or waking up. Its most frightening aspects stem from the way it blurs the line between sleep and wakefulness: people may sleepwalk, scream in terror, act out violent dreams, experience vivid hallucinations, or awaken unable to move during sleep paralysis while feeling the presence of a threatening figure nearby. These episodes can feel intensely real, involve a loss of control, create memory gaps, and sometimes lead to injury.