Black Trillium by Marion Zimmer Bradley Book

Ruwenda is a pleasant, peaceful land-but the magic of its guardian, the Archimage Binah, is waning. Binah must pass along her protectorship to the triplet princess of Ruwenda. She bestows upon the infant girls the power of the rare and mystical Black Trillium-badge of the royal house, symbol of an ancient magic. While the sisters blossom into beautiful young women, neighboring Labornok use a dark magician to sunder Binah’s protection. As invaders pour into Ruwenda, the Archimage orders the princesses to flee-and changes them to search for three magical talismans which when brought together will be their only chance to regain their kingdom and free its people. Each must accomplish her task separately-and to succeed, each must also confront and conquer the limits of her own soul.
This book was written by Marion Zimmer Bradley and Julian May and Andre Norton.