Aatxe

Aatxe is an evil spirit in the folk mythology of the Basque people. His name is literally translated as "Young Bull", and he is sometimes known as Etsai. He is a cave-dwelling spirit who adopts the form of a young red bull, but being a shapeshifter, sometimes takes the shape of a man. At night, more so in stormy weather, he arises from the hollow which is his lair, also known as Euskal Herria. He attacks criminals and other mean people. He also protects people by making them stay home when danger is near.
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[Basque] A Basque evil spirit in the form of a bull, but occasionally in the form of a human being. At night, especially during stormy weathers, he emerges from his cave. Also named Aatxegorri (young red bull).