Hypnopompic hallucinations can happen with sleep paralysis, when body paralysis lingers during the waking process, leaving people conscious but immobile. For people who experience sleep hallucinations, the period between consciousness and REM sleep is shorter. They are connected to sleep paralysis, which can be downright scary. You may even think you’re being attacked—a horrifying experience people call sleep paralysis demons. Rein feels lucky that he doesn’t have the scary version of sleep paralysis, even though he does have hypnopompic hallucinations.