This is the final volume in the 'Avalon' series.
Helena. Beautiful, young enigmatic. She's a daughter of the Holy Isle who became a Christian Saint and her heroine of Welsh legend. In 296, the emperor Contantius comes to Britain and falls in love with Princess Eilan, known as Helena to the Romans. She is also the daughter of King Coel and the high Priestess of Avalon. Helena sees a chance to marry the bloodlines of ancient royal families, and their myths and traditions. But she has to contend with the politics of Rome, the ill fortunes of war and the irresistable rise of a powerful new religion . . .
