The Outlanders (The Lon Tobyn Chronicle, Book 2) by David B. Coe

The Children of Amarid now know that invaders from Tobyn-Ser's sister land of Lon-Ser are responsible for the deadly attacks on their people. But their Order is paralyzed by infighting and indecision, and it is only a matter of time before the next invasion begins.To prevent this a rebellious young mage names Orris undertakes a journey into the darkest heart of Lon-Ser. There he will find technological marvels and industrial terrors unlike anything in Tobyn-Ser, a long-lost splinter of the Children of Amarid, and an extraordinary woman whose actions will either save him--or plunge both lands into all-out war.