The Children of Magus - The Minder's War, #3

Magus is dead and his bastion has fallen. Enslaved by the minder Frog, Deanne must choose: live a life in blissful servitude, or defy the minders and discover the mystery behind her imprisonment and Magus's black castle. But the young girl Paige is alive somewhere within Deanne's prison, and she possesses the raw talent to control all of Magus's alien machinery. Deanne only has to find her and convince her to fight. Outside the castle, the Goddess continues to scheme.
As she works to destroy all who would stand against her, more minders turn on her. The destruction of the black castle would send a clear signal: to defy her means death.