The Nocnitsa, or "Night Hag

Hag

A hag is a wizened old woman, or a kind of fairy or goddess having the appearance of such a woman, often found in folklore and children's tales such as Hansel and Gretel. Hags are often seen as malevolent, but may also be one of the chosen forms of shapeshifting deities, such as the Morrígan or...

", in Polish mythology

Polish mythology

Polish mythology comprises beliefs and myths of ancient Poland, including witchcraft and elements of Paganism.An early Polish settlement featuring an allocated place of pagan worship, which is located near the ancient complex of Poganowo not far from the Polish coast of the Baltic Sea, was...

, is a nightmare

Nightmare

A nightmare is an unpleasant dream that can cause a strong negative emotional response from the mind, typically fear or horror, but also despair, anxiety and great sadness. The dream may contain situations of danger, discomfort, psychological or physical terror...

 spirit that also goes by the name Krisky or Plaksy. The Nocnitsa is also present in Russian, Serbian

Serbian folklore

Serbian folklore is the folk traditions among ethnic Serbs. The earliest examples of Serbian folklore are seen in the pre-Christian Slavic customs transformed into Christianity.-Folklore:...

 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

Bulgaria

Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

 as Gorska Makua.

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

Sleep

Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...

.