Mares or "Nightmares" are spirits or goblins in Germanic folklore which rides on people's chests while they sleep, bringing on bad dreams ("nightmares"). The mare is attested as early as in the Norse Ynglinga saga from the 13th century, but the belief itself is likely to be considerably older. As in English, the name appears in the word for "nightmare" in the Nordic languages (e.g. the Swedish word "mardröm" literally meaning mara-dream, the Norwegian word "mareritt" literally meaning mare-ridden or the Icelandic word "martröð" meaning mara-dreaming repeatedly). The mare is similar to the mythical creatures succubus and incubus, and was likely inspired by sleep paralysis.
- The word "mare" became another name for horses, especially for she horses.
- the phenomena of the "Mare" is now explained via the medical condition known as Sleep Paralysis.