Legend of the Ravenstone. Ravenstone, #1

They were destined for failure. When William, a mysterious and manipulative wizard, learns the deadly Ravenstone has been uncovered by a self-proclaimed regent known as the Priagent, he hastily assembles a group of mismatched travelers to steal the stone and deliver it to safety. The Ravenstone is an ancient relic-a remnant of a battle between gods-and it has the power to unravel magic. The unlikely company sent to retrieve it consists of Arcturus, an exiled politician with a fondness for wine, Kariayla, a winged slave girl on a quest for redemption, Jinx, an unlucky thief and his imp counterpart, and Hawkwing, William's personal spy, at the helm.
Distrust, secrets, and inexperience threaten to compromise the mission as the group is forced to travel in the company of the enemy. Doubt turns to the wizard who employed them on this precarious quest-the quest to obtain a mythic source of dark power: the Legend of the Ravenstone.