Who is Baba Yaga from Women Who Run with the Wolves and what is their importance?

Baba Yaga is the Wild Woman as the wise old woman, in some traditions called the Crone. She appears early in the book. She initiates a much younger one, named Vasalisa. She is depicted as old, ugly, very intimidating and extremely powerful. A girl child, who is mature within the range of childhood, is sent off to meet this Old Lady, by malicious step relatives, who wish to end her life. However they have masked their utter malice by couching their wish in the language of sending her upon a quest with a task to find the family another source of fire so they can re-light their family hearth.