I'm not ratting on pagan religion, I'm speaking from a psychological perspective here.  All three are sleep paralysis.  It is a problem with the physiology of the brain during sleep.  It's caused by an inactive pons, an area in the brain stem, during periods of post-sleep where it should be inactive.  The pons is responsible for paralyzing your muscles when you sleep as to prevent you from acting out your dreams.  When it is inactive as you awake, you can't move.  It can be quite frightening because your breathing rate is suppressed and it sometimes feels like there is someone pressing down on your body.  That's where the myth of the incubus/succubus comes from.\n\nScott, you're full of it.  no offense.  That's such a primitive way to characterize a sleep/brain disorder.