no mercy - you are not awake though...you are dreaming you are awake - you can look around at your bedrrom and beleiev your eyes are open, but you are so familar with your bedroom that your mind can easily imagine it in detail, so it fools you...
the shadowy figures etc are either simple imagination or you have very slightly opened your eyes, just enough to see blurry shapes in the darkness...they will mutate and your mind will interpret them as negative or sinister because the paralysis is a generally unpleasant and frightening experience.
you cannot move because you are asleep and your body is preventing you from acting out the dreams - ie, sleepwalking and talking etc - people who do these things have a malfunction in the mechanism that prevents them acting out dreams.
same way you can dream you are weeing - usually because you have a full bladder - but you dont actually wet your bed, no matter how bursting you are or how much you dream you are - your body knows better and that you are asleep, so stops you doing it. (unless you are drunk)
it is called lucid dreaming and astal projection - being asleep but becoming acutely aware you are in a dream, and so feeling and seeing everything.
some people believe they actually leave their bodies and astral project - it certainly feels like you are...
it can supposedly be triggered by learning a 'switch' - such as training your mind to think of lucid dreaming whenever you, for instance, drink something - you think to yourself 'am i dreaming?' wheneevr you drink and if, in a dream, you drink somethign you are reminded of this question, you will begin the lucid dream.
you can make your own trigger of course... something that forces you to ask yourself this question - am i dreaming?
i have had some wonderful experiences...you feel everything, wind in hair, cold, rain, etc... unfortunately it doesnt last long because you become too aware you are lucid dreaming and your conscious mind wakes up...
i have had a few horrible ones... one where i opened my eyes just at the moment a car was passing outside and the lights shining through the window made the shadow of the yucca plant appear to be a 2 foot spider running across the wall...
i had seen that same image a hundred times while awake ...but in my half dreamstate, it had legs that ran and a body and was fully detailed.
i was in the hallway before i had a even realised what had happened.