Mare

A Mare is a creature originating from Scandinavian folklore. Described as some kind of evil spirit or goblin, this monster is said to "ride" its victims, laying upon a person's chest while they sleep. The Mare's presence causes the sleeping victim to experience nightmares while the creature sucks their life energy. This has led to Mares being compared to succubi, demons that feed on the life energy of men during sexual intercourse.

The mare was also believed to "ride" horses, which left them exhausted and covered in sweat by the morning. She could also entangle the hair of the sleeping man or beast, resulting in "marelocks".

Trivia

 * The word "nightmare" comes from "mara", the Old High German term for "mare". This is because after the mare has ridden its victim the person will feel its presence in the form of tormented dreams, or nightmares.