Enchantress Mine by Bertrice Small

Flame-haired Mairin of Aelfeah was a ravishing beauty who caught the attention of three extraordinary men—Basil, Prince of Byzantium, who taught her love’s mysterious secrets; Josselin of Combourg, a gallant knight of William the Conquerer; and Eric Longsword, the powerful Viking whose tragic love for Mairin would mark her forever. To these men, Mairin was the Enchantress— and in a world gone mad with savage war and fierce desire, only their love could save her.