The Nightmare was likely inspired by an interpretation of dreams based on Germanic folklore, in which demons possessed people who slept alone. In these stories men were visited by horses, and women were ravished by the devil. The woman is surmounted by an incubus; a mythological demon who lies upon sleeping women. It has remained Fuseli's best-known work. With its first exhibition in 1782 at the Royal Academy of London, the image became famous. After that Fuseli painted at least three versions.
To see the original: https://bit.ly/2VREsHx