I looked up "Night Hag" on google, and found this, if somewhat short description :
"Night hag, a witch supposed to wander in the night. ..."
I also found something about "Night Hag attacks", which seem to be some form of Psychic attack that people experience.
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Night Hag Attacks
Night Hags or Mara are a really popular phenomenon nowadays, aren't they? I mean, just about everywhere I look lately people are talking about them. Don't think I ever experienced it myself, that I know of. But I do agree that it's silly to think that a night hag attack sufferer could confuse sleep apnea or other physical phenomena with a real night hag attack. It's just two different things altogether. Still, this is just the same thing as people saying psychic attacks aren't common occurrences, or people saying all people who claim they are psychic or have experienced psychic phenomena are just psychosomatically ill. What people have not experienced, they tend to disbelieve, and rationalize, and explain away. Most people are not ready to face the Real World, to borrow a phrase from Nancy Collins' Sonja Blue books :)
Well I won't say much about Night Hag attacks since most people know of them already. Basically the signs are a crushing weight on your chest, difficulty breathing, paralysis, probably a lot of fear *grin* and a feeling as though you are being drained or weakened. These attacks can be carried out by psyvamps who are able to travel astrally, or by astral psyvamps (ie. disincorporate psivamps).
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There was also a picture of what is described as "The Night Hag visiting the Lapland Witches" :

I don't know if the Psychic attacks and the actual Night Hag witch figure are the same thing or not.
Lord_Frieza - is it these Night Hag pychic attacks mentioned above that you have experienced ?
They sound unpleasant to say the least. :(
Oh, and welcome to the forum by the way. :)
:sk