The Tower on the Rift (The View from the Mirror #2)

Once there were three Worlds, each with its own human species. Then, fleeing out of the void came a fourth species, the Charon. Desperate and on the edge of extinction, they shifted the balance between the Worlds forever. Now Karan, a young Sensitive who carries the blood of all three Worlds, has come into possession of the Mirror of Aachen, which holds the power to heal-or destroy-World relations. But as war rages, Tensor, the leader of the Aachim people, steals the mirror and flees into the wilderness with the lovely young Chronicler, Llian, leaving all to wonder how they plan to use their powerful new magic.