In a world cleaved in two by a massive barrier of perpetual darkness, a young soldier uncovers a power that might finally unite her country. But as she struggles to hone her power, dangerous forces plot against her. Thugs, thieves, assassins and saints are at war now, and it will take more than magic to survive.

Three people's fates are interwoven in the Battle of the Teutoburg Forest in 9 A.D., during which Germanic warriors halt the spread of the Roman Empire.