Rift in the Sky — Julie E. Czerneda

Julie E. Czerneda's Trade Pact Universe trilogy introduced the Clan, refugees from the world of Cersi who built an empire few people even knew existed.

The Stratification trilogy -- of which RIFT IN THE SKY is the final volume -- returns to an earlier point in the Clan's history, before they left Cersi. Known as the Om'ray, they are divided into widely scattered tribal Clans, constrained from advancing beyond a certain point by two powerful races -- the Oud and the Tikitik.

RIFT IN THE SKY opens at a critical moment for the world of Cersi and the Om'ray Clans. As more Om'ray master the Talent of moving through space via the M'hir dimension, their newfound freedom threatens the delicate balance between Cersi's three races. At the same time, it causes a perilous division within the Clans themselves between those who do and don't have this Talent.

The crisis escalates when outsiders from Trade Pact space discover archaeological treasures left by the legendary Hoveny civilization. As Cersi becomes the target of interstellar raiders, the Om'ray realize that any hope for survival lies in using the forbidden power of the M'hir to find a haven where their enemies will never look for them....