In Russian and East Slavic folklore, Baba Yaga is a supernatural being who appears as a deformed or ugly old woman. She is called Baba Yaga the Bony Leg. Sometimes, she has a bony leg; other times, a leg made of iron or other materials. She has an iron nose, fangs for teeth, barely any hair. She senses the "Russian scent" of those who visit her. She is terrifying.
Baba Yaga is portrayed as a witch living deep in the Russian forest in a hut that stands on chicken legs. Sometimes, the hut stands on goat legs or ram horns. Around the hut is a fence made of human bones with human skulls at the top. When Baba Yaga lies inside her hut, she does so on the traditional Russian pech stove, her body stretched out from one corner of the hut to the other. When Baba Yaga needs to go anywhere, she flies. But not on a broom. She uses a mortar and a pestle, sweeping her tracks with a broom.
Baba Yaga is different from the witches of western fairy tales. In many ways, she is an enigma, an entirely mysterious and baffling personality. She is not always a villain. She can be a donor or entirely ambiguous. She frequently helps the heroine or hero on their journey, and is often seen as a type of mother figure or moral arbiter. Frequently, she prepares maidens for a life of domesticity and motherhood, particularly if they are "good," "smart," and "polite." When it comes to young men, Baba Yaga prepares them for a quest in which they seek their missing bride, i.e., their betrothal and eventual marriage. In contrast to young maidens, the young men frequently boss her around, demand food and a bath, and treat her disrespectfully. They are rewarded for this "masculine" behavior by being given directions or magical objects to help them on their quest. This shows the moral differences between women and men in the conservative Russian society in which Baba Yaga tales first appeared. Not surprisingly, Baba Yaga is often harder on women. If a woman is "bad," "stupid," and "impolite," the witch will not be kind or helpful. Death is often the end result.
The Baba Yaga we know is likely an invention of the fairy tales that were written down and disseminated beginning in the 18th Century. However, there is evidence that she existed long before then. Before Christianity came to Russia, Baba Yaga was a goddess worshipped by Slavic pagans. Some say she was the Earth Mother Mokosh herself. Mokosh was the protector of women's work and destiny, and the only female deity whose idol was erected by Vladimir the Great in his Kiev sanctuary along with statues of other major gods.
Baba Yaga is often associated with wildlife and animals, the weather, the seasons, day and night, and other natural phenomena. She is frequently associated with various animals, whether snakes, birds, or chickens and hens. In Vasilisa the Beautiful, one of the most famous fairy tales that features Baba Yaga, three riders serve Baba Yaga: A white rider, Day; a red rider, Sun; and a black rider, Night. In some tales, Baba Yaga has keys to the moon and stars in her hut. In other tales, she is a cloud, she is winter, she is a storm. In still other tales, she is the boundary between the living and the dead. In fact, her hut stands on the border between this world and the next, and it is only after arming themselves with her charms that heroes can cross this boundary in quest for their beloveds.
Sources:
Baba Yaga, Wikipedia
Vladimir Propp's folktale morphology
Baba Yaga: The Ambiguous Mother and Witch of the Russian Folktale, Andreas Johns
Baba Yaga Laid an Egg, Dubravka Ugresic
Russian Fairy Tales, Aleksandr Afanasyev
Alkota thanks very much Ms. Olesya Salnikova Gilmore, the Russian folklore analyst and fairytale researcher for preparing this information.