Tiassa by Steven Brust

Once, Vlad Taltos knew his trade: he killed people for a living. That skill got him his foothold in House Jhereg, running the rackets for a chunk of urban Adrilankha. Later things happened, leaving Vlad a changed man, on the run from the Jhereg, and frequently involved in the affairs of Dragonlords, Empresses, and even Jenoine. Far more involved than the average short-lived human. Meanwhile in the very distant past, one of the gods fashioned an artefact - a silver tiassa. To Devera the Wanderer, it's a pretty toy to play with. To Vlad, it's a handy prop for a con he's running. To the Empire, it's a tool to be used against the Jenoine. And to the Jhereg, it's a trap to kill Vlad. As it happens, however, the silver tiassa has it's own agenda.