Mora are mostly malevolent folkloric beings associated with sleep that in some form or another can be found throughout Europe.
In Polish folklore, mora are the souls of living people that leave the body during the night, and are seen as wisps of straw or hair or as moths. In certain Slavic languages, variations of the word mora actually mean moth (for example, see Czech word můra).
In Serbian, "mora" refers to a "nightmare". Mora or Mara is one of the spirits from ancient Slav mythology. Mara was a dark spirit that takes a form of a beautiful woman and then visits men in their dreams, torturing them with desire, and dragging life out of them. Other Slavic names were nocnica, night woman, or ejjeljaro, night-goer.
In Germany they were known as mara, mahr, mare, in Romania they were known as Moroi. In Slavic countries the terms included mora, zmoras, morava and moroi; in France, such a witch was the cauchemar. Hungarian folklorist Éva Pócs traces the core term back to the Indo-European root moros, death.
Like other trance practitioners, mora witches traditionally owed their abilities to being born with a caul. In their metamorphosed form they could fly through the night, walk on or hover above water and travel in a sieve. Dead mora witches were said to return as ghosts.