Twist, I see you met *old hag* (i.e., sleep paralyis).

Old Hag is caused by sleep paralysis lingering after waking. Sleep paralysis happens during REM dreaming, and prevents you from acting out your dreams by blocking motor signals from your brain. The classic symptoms are - unable to move, a feeling of weight on your chest and/or unable to breath, a sense of a presence, fear or panic, and some vague (usually greyish) object in the centre of the visual field which is often interpreted as a person (or nowadays, an alien). The "Old Hag" name arose from people putting the symptoms together to form the interpretation that an old hag was sat on your chest, pinning you to the bed.

Below is my one and only experience with *old hag*:

http://www.dreamviews.com/community/...ghlight=hag%2A