Wizardoms: Eye of Obscurance by Jeffrey L. Kohanek

A clever thief, a determined acrobat, and a troubled dwarf are joined by an old storyteller as they attempt the impossible: Assassinate a wizard lord. Their slim hope relies on the enchanted amulet, the Eye of Obscurance. These unwitting pawns are embroiled in a contest of wizards. The stakes: The fate of the world.