The Dagger and the Cross — Judith Tarr

In the time of the Crusades, in a world at war, a prince of immortal lineage and a spirit of fire who was once an Assassin prepare to celebrate a royal wedding. But he is Christian and she is Muslim, and there are those who hate them not only for their disparate faiths but for their power and magic.

From the holy city of Jerusalem to the bitter battlefield of Hattin, from Saladin's Damascus to the Crusaders' fortress of Acre, the tides of war sweep the lovers apart. Even magic might not be enough to save them, or the kingdom to which they have both pledged fealty.

Sequel to ALAMUT.