The Argument of Empires (The Corrossan Trilogy Book 1)

Betrayal, Intrigue, War.
They are the cause of every nation's fall. But the Corrossan Empire is no simple nation: it is a dynasty. It alone has stood for four hundred years, led by the ageless Hadan, conqueror of a dozen peoples and a pair of continents.
But at the height of its power, the Empire is assailed from within. Hadan is dying, and forces move in the shadows, seeking to speed along his passing. Cracks form, rebellions fester, and a two year war against the monstrous Cutarans grinds to a halt.
Grith finds himself shoved into a world he wants no part of, ripped from his home by the very men responsible for sending his parents to their deaths. But with capture comes power, a power that will make Grith feared by all those who cross him.
As punishment for a rebellion she can hardly remember, Kareen has traveled halfway across the world to pay her taxes at Emperor Hadan's feet. It is a small price to pay, she tells herself, so that her noble family can keep its lands and freedom. But now she must ride headlong into a warzone, and face down the Cutaran Warchief Xisa.
Both will decide the fate of empires: Preservation or Destruction.