I feel like such a tard asking this:
What is “old hag” 
Moved from Gen :moh:
I think its like an old mean lady that you don’t like
https://community.ld4all.com/t/the-big-sleep-paralysis-and-old-hag-topic/10897
It’s that feeling that someone is sitting on your chest while you’re dreaming/waking up, making it hard/impossible to move. The “old hag” is sitting on your chest.
ooooooo I didn’t know it was sleep related 
“old hag” is a folklore term for frightening Hallucinations during Sleep Paralysis.
Must not sit on your chest, but may be… Also can sit next to your bed or stand in your room or something, looking like a devil or “Mr. Death” or something…
It’s a nacht mara, (which is where the term nightmare comes from) A Mara is a malignant female being, I think it’s of scandinavian origin.
You may have also heard of a Succubus, which is the same thing, a female demon who sits on the chest or chokes people in their sleep.
Of course what it actually is a sleep paralysis, or more precisely the feeling that there is another presence in the room - usually malignant, invoking a sense of fear - whilst under the effects of sleep paralysis.
edit - Out of shameless self promotion I’m putting a link in to my poem on the subject, I experience it a lot and think this is a fairly accurate description.
https://community.ld4all.com/t/burning-idles-mind-myths/25614&&start=15
Plugged ;p