The Towers of Samarcand (Rise of Empires)

A select band of soldiers led by Luke Magoris are given the mission of persuading Tamerlane to defend Constantinople. The great conqueror must turn his forces to the West to fight the Ottomans, who otherwise would destroy Constantinople and the Byzantine empire. Luke, torn away from the woman he loves and all he knows, is trained as a Mongol warrior to impress Tamerlane and his army before joining his fellow Varangian guards, descendants of the men who once brought a vital treasure out of Constantinople. It is this treasure, some say, that can still save the empire - uniting the Christian churches of the east and west in one final triumphant crusade to smite the Ottomans.