The Wind that Sweeps the Stars - Greg Keyes

A taut high fantasy as an assassin must destroy an empire from within, eliminating wizards, their demons, and even the emperor. For the lives—for the very souls—of her people, she must succeed within a single day, or her homeland will be destroyed.ALONE AGAINST AN EMPIRE.When Yash of Zeltah arrives in the fortress city of Honaq, she is greeted as a barbarian, a simple pawn. Her marriage to prince Chej has been arranged, they say, to avert war. Yet she knows the truth, for the armies already ravage the land.A skilled and deadly assassin, there is more to Yash than any might suspect. Before another day can pass, she must defeat the masters of the nine towers—the plagues, magics, and monsters they control, the soldiers they command. Without raising an alarm, she must kill all who oppose her—even the immortal emperor. The lives and souls of Zeltah, the people and the land upon which they live, all depend on it.