Wind on Fire Trilogy Book Two, The Slaves of the Mastery (mass market)

The people of Aramanth are finally free of the Morah, the evil power that controlled them for generations. But a ruthless attack by soldiers from a distant land destroys the city, and its people are driven off as slaves. During the invasion, Kestrel and Bowman are separated for the first time in their lives. Bowman becomes a slave of the Mastery. Kestrel escapes, then sets off to avenge the enslavement of her family. As the twins embark on their parallel adventures, their mother's prophetic dreams reveal their true identity and their dangerous fate. Bowman's mind power and Kestrel's fierce spirit are soon joined once again to fight for the freedom of their people.