The Guardian and The Queen (The Horizon Cycle, #5)

He escaped one prison—only to find he holds the key to something far worse.

Aes thought freedom would bring peace. But with his Guardian, Trea, lost in the void and an ancient Dowager Queen demanding he open a path to another world, Aes finds himself caught in a game far older, and far deadlier, than he imagined.

Meanwhile, Olli Speare has waited two years to find someone who can open the door back to Horizon, and to Brend, the boy she lost. Aes may be the only one who can get her there. But ...