Slaves of the Mastery — William Nicholson

KESTREL AND BOWMAN risked their lives to restore the key to the wind singer. Now, five years later, the people of Aramanth are finally free of the Morah, the evil power that controlled them for generations. But with the new kindness has come weakness, and Aramanth lies undefended-- unable to resist an attack by soldiers from a distant land. The city is burned to the ground, and its people driven off as slaves.

During the invasion, the twins are separated for the first time in their lives. Bowman becomes a slave of the Mastery, a city where the rulers live in luxury and beauty. 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 dangerous fate. Bowman's mind power and Kestrel's fierce spirit are soon joined again to fight for the freedom of their people. As they plan to destroy the Mastery, however, they must also face the evil Morah once again.