The Kingdoms of Dust

With her master dead and her oaths foresworn, necromancer and spy Isyllt Iskaldur finds herself in exile. Hounded by assassins, she seeks asylum in Assar, the empire she so recently worked to undermine.
Warlords threaten the empire's fragile peace, and the empress is beset by enemies within the court. Even worse, darkness stirs in the deep desert. Ancient spirits long held captive are waking -- spirits that can destroy Assar faster than any army.
Accompanied by an outcast jinn, Isyllt must travel into the heart of the desert to lay the darkness there to rest once more. But her sympathies are torn between the captive spirits and the order of mages sworn to bind them. And whichever choice she makes could raze the empire to dust.