Fortress of Dragons (Fortress Series #4)

It started long ago, in a tower at the Eye of Time, as a war between the shadowy Immortals who came long ago. Tristen is a Shaping, both more and less than human, who turned back sorcery's tides in the legendary battle of Lewenbrook that brought his friend Cefwyn the burden of a kingdom, and the light of love. Now the Lines that hold the world in place are shifting once again, and Cefwyn's peril is Tristen's call to arms. But even Tristen's double-edged sword cannot cut through the knot of this new challenge, for he is facing more than a mere pretender to his friend's throne.