City of a Million Legends (First Lifewave) by Jacqueline Lichtenberg

Older and wiser, the humans and nonhumans of Molt Brother now suffer the consequences of their actions. They have stirred the karma of their lifetimes lived billions of years ago - when they were responsible for the destruction of a Galactic Civilization, the First Lifewave. Now they must seize the object of power that corrupted them the first time - to keep it from the hands of an implacable enemy. Can they resist its lure and save the Second Lifewave?