The Nocnitsa, or night hag, of Russian, Polish, Serbian and Slovak folklore is known to torment children at night, and a stone with a hole in the centre is said to be protection from her. In some regions a mother will place a knife in their children's cradles or draw a circle around the cradle with a knife for protection. This is possibly based on the belief that supernatural beings cannot touch iron.
The Noncnitsa is known to sit on her victim's chest and draw their life energy, draining it until they cannot go on (because of this many refer to this creature as a type of vampire) and she will continue visiting. To stop her, the victim has to fight back and do not give in to her.
Many say she visits when you sleep on your back with your hands on your chest. This is called sleeping with the dead. The night hag is made of shadow but the most noticed part of her is the eerie red glow of her eyes and the horrible screech of her voice, the part below her waist is all shadow. Her smell is of moss and dirt from a forest said to be where she lives, and at times her stench can infiltrate your dreams, or linger in the room after her visit. She is also known as a demonic spirit who feeds off your darkness (namely depression and sadness), this makes the night hag stronger, more powerful and makes her harder to get rid of.