Nocnitsa (folklore)

The Nocnitsa, or "Night Hag", in Polish mythology, is a nightmare spirit that also goes by the name Krisky or Plaksy. The Nocnitsa is also present in Russian, Serbian and Slovakian folklore. She is known to torment children at night, and a stone with a hole in the center is said to be a protection from the Nocnitsa. Mothers in some regions will place a knife in their children's cradles or draw a circle around the cradles with a knife for protection. This is possibly based on the belief that supernatural beings cannot touch iron.

Folklore
The Night Hag is known to sit on your chest and draw your life energy, drawing it until you can not go on (because of this many refer to Nocnitsa as a type of vampire) and she will continue visiting. To stop the Night Hag, you have 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 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.

She is known in Bulgaria as Gorska Makua.

The Night Hag is almost certainly linked to the common apparition seen during the hypnagogic state of sleep.