City of Bones

Khat, a member of a humanoid race created by the Ancients to survive in the Waste, and Sagai, his human partner, are relic dealers working on the edge of society, trying to stay one step ahead of the Trade Inspectors and to support Sagai's family. When Khat is hired to find relics believed to be part of one of the Ancients' arcane engines, they are both reluctant to become involved. But the request comes from the Warders, powerful mages who serve Charisat's Elector. Khat soon discovers that the deadly politics of Charisat's upper tiers aren't the only danger. The relics the Warders want are the key to an Ancient magic of unknown power, and, as all the inhabitants of Charisat know, no one understands the Ancients' magic.