Power: The Girl in the Box, Book 10 (Unabridged‪)‬

Sienna Nealon seems like a woman beaten. Imprisoned by her enemies and facing the extinction of her entire race, she is up against overwhelming odds. But overwhelming odds have never stopped her before. 

With time running out, Sienna must face her fears, face her foes, and then go up against the single most powerful man in the world—Sovereign—in order to save her world from complete and total destruction.