Baba Yaga is a hag from Slavic folklore. She lives in the forest in a hut that stands on chicken legs, and flies around in a large mortar.
Baba Yaga is one of three sisters, and appears as an ugly old woman with a prominent nose. She is usually described as a frightening, evil figure, but is more ambiguous in some stories. She was first mentioned in 1755 by Russian writer Mikhail Lomonosov, and has since become an enduring figure, not just in Eastern Europe, but worldwide.