Nøstekatt
The troll cat (Norwegian: trollkatt, also nøstekatt) is a witch's familiar in Scandinavian folklore, a supernatural cat sent by a witch to steal milk from neighbours' cows. It may travel in the form of a ball of yarn (trollnøste), and harm done to it is shared by its witch, who must bury it with her. Fisherfolk and farmers feared its milking raids on cattle.