Synposis from the back of the book:
Every two thousand years, parallel dimensions collide on the world called Raisa, bringing a tide of death and destruction to all worlds but one. Multiple worlds battle their dopplegangers for dominance, and those who survive must contend with friends and enemies newly imbued with violent powers.
Now the pacifist country of Dhai's only hope for survival lies in the hands of an illegitimate ruler and a scullery maid with a powerful – but unpredictable –magic. As their dopplegangers spread across the world like a disease, a former ally takes up her Empress’s sword again to unseat her, and two enslaved scholars begin a treacherous journey home with a long-lost secret that they hope is the key to the other worlds' undoing.