Mare (folklore)
A mare (Old English: mære; Danish, Norwegian: mare; Swedish: mara; Polish: mara, zmora; among many others) is a malicious entity in Germanic and Slavic folklore that sits, walks, or "rides" on people's chests while they sleep, bringing on nightmares. When placed on the victim's chest, it is said to have a suffocating effect, and can lead to cold sweats or sleep paralysis.