Shadow on the glass. Ian Irvine. 1998.

Once there were three worlds, each with their own human species. Then, fleeing out of the void came a fourth species, the Charon. Desperate, on the edge of extinction, they changed the balance between the worlds forever.

Karan, a sensitive with a troubled heritage, is forced to steal an ancient relic. But it turns out to be the Mirror of Aachen, a twisted, deceitful thing that remembers everything it has ever seen.

At the same time,mLlian, a brilliant chronicler, is expelled from his college for uncovering a perilous mystery. Thrown together by fate, Karan and Llian are hunted across a world at war, for the Mirror contains a secret that offers each species survival.........or extinction.