Who is Lady of the Forest from Daughter of the Forest and what is their importance?

Lady of the Forest is one of the Fair Folk. She serves as Sorcha's mentor, warning her of the dangers in the path she is about to set out on, and telling her how to reverse the curse on her brothers. The Lady of the Forest, along with other members of the Fair Folks, seems to be playing a game with Sorcha and her family. However, they also give her a great reward in helping her find true love with Red.