The Mare is an old Norse monster that rides on people's chests while they sleep, bringing on nightmares.
The word mare comes from the old Norse word "Mara" which different variations make up the word nightmare in various languages. Examples of this of course include nightmares. The Swedish word "mardröm" literally translates to "mare dream", the Danish word "mareridt" directly translates to "mare ride" and the Icelandic word "martröð" means "to be stepped on or trodden on by a mare" .
Mirrors of the Mare can be seen throughout many cultures and seems to be a way to explain nightmares and sleep paralysis by ancient cultures .
The mares procedure varies slightly throughout all cultures. Some things tied to the mare are torture, strangling, draining life, and rarely even eating flesh.
: Bjordvand, Harald and Lindeman, Fredrik Otto (2007). Våre arveord. Novus. ISBN 978-82-7099-467-0. pp.719-720