Your experience is not that uncommon - your symptoms are consistent with sleep paralysis with conscious or lucid dreaming (sometimes called hallucinations, but in this sort of case associated with a partial dream state).
Normally when you go into dreaming sleep, your voluntary muscle control is 'disconnected' to stop you acting out your dreams. As sleepwalkers demonstrate, this doesn't always work properly, but sometimes the opposite effect occurs - dream paralysis while conscious.
Your conscious awareness is generally only partial during dreams - the dept of consciousness can vary, and it's possible to be fully conscious while dreaming (I've had this on a few, memorable, occasions).
It's less common to become conscious while still in dream paralysis - it typically comes around the time of normal waking, and is often accompanied by a sense of weight on the chest - and sometimes personified as an evil presence (e.g. the 'Old Hag'). Bedroom 'alien abductions' are contemporary versions of this effect.
You seem to have experienced both waking sleep paralysis and a partial dream state. As George says, if it was the middle of the night, i.e. dark, you probably wouldn't be able to tell if the demon's eyes were actually black or not; this detail suggests a dream state, although your eyes can be open and seeing the room for real.
Here's an article describing the general experience and it's cultural interpretations:
The Demon on your Chest, and Other Terrifying Tales of Sleep Paralysis. Here's the published paper it's based on:
Sleep Paralysis in Brazilian Folklore and Other Cultures: A Brief Review.
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Sleep paralysis (SP) is a dissociative state in which an individual, upon going to sleep or waking up, is unable to move (Mahowald et al., 2011). SP is accompanied by frightening, and often fantastic, hallucinations and delusions (Dahlitz and Parkes, 1993), thus different societies interpreted it under a supernatural or metaphysical perspective (Hinton et al., 2005)."