Mara

A Mare (or Mara) a malevolent spirit from Germanic and Scandinavian folklore... was believed to creep into people's rooms at night, sitting heavily on their chest and suffocating them in their sleep. These nocturnal visitations caused terrifying dreams, sleep paralysis, and the eerie sense of being watched — giving birth to the modern idea of the "nightmare". To protect themselves, people would scatter rice or sand by the window — not as a barrier, but as a trap for her obsessive mind. Cursed to count every grain, she’d spend the night distracted, unable to enter.