Fortress of Eagles - C. J. Cherryh

Tristen is both more and less than a man. A summoning, a shaping, he was brought to life by a wizard, to serve a king yet to be crowned.
Now the wizard is dead: a united Ylesuin, and a peace this land has never known. Cefwyn needs his only friend, this young man of mysterious origins who is more brother than vassal. He relies on Tristen, and trusts him though he knows not why, as he plans the war that will bring his dream to pass...or bring ruin upon them all.
The eagerly awaited sequel to her acclaimed Fortress in the Eye of Time, C.J. Cherryh's newest high fantasy triumph is an epic saga of destiny and intrigue in a magical world as wondrous, and as real, as our own.