The Final Key — Catherine Asaro

The Final Key is the second and concluding part of the story known as Triad, which began in Schism. Schism ended with the Skolian Empire torn asunder by personal conflict within the royal family, as Sauscony defied her father and joined the Skolian military.

Now in The Final Key, the Skolian Empire comes under all-out assault from its nemesis, the Euban Concord, who have undermined the Skolians via subterfuge and assassination, leaving them ripe for conquest. The war is devastating. And the Skolian Empire's only hope is Sauscony, a young woman barely out of her teens who hasn't even completed her training as a cadet.

The fate of a vast interstellar empire rests in her untested hands.