Two hundred years after the Forbidding was broken, Santhenar is locked in war with the Lyrinx – intelligent, winged predators who will do anything to gain their own world. Despite the development of battle clankers and mastery of the crystals that power them, humanity is losing. Tiaan, a lonely crystal worker in a clanker manufactory, was experimenting with an entirely new kind of crystal when she began to have extraordinary visions. The crystal had woken her latent talent for geomancy, the most powerful of all the Secret Arts – and the most perilous. Now Tiaan is leading her people in a last desperate stand against the Lyrinx . but if they are to survive she must master her new powers or be destroyed .