Inspired by the oil painting "The Nightmare", by Henry Fuseli (1781), this is a personal recreation of the piece with a few subtle changes and more emphasis on the horse demon.
The Nightmare is an example of Gothic art and representation of Germanic and Slavic folklore. It was believed that nightmares and sleep paralysis were caused by a demonic Mare taking possession of the body or standing on their chest while asleep.
The original painting by Fuseli may also have been an allegory for the unconscious mind and its sometimes frightening characters that often visit us in dreams.