Shadowrise (Shadowmarch, #3)

With King Olin imprisoned and Prince Kendrick slain, the royal twins Barrick and Briony have been forced to flee their homeland. But both families and nations can hide dark and terrible secrets. Even if Barrick and Briony survive learning the astonishing truths at the heart of their own family and of Southmarch itself, they must find a way to reclaim their kingdom and rescue their home-from traitors, tyrants, a god-king, and even the angry gods themselves.