The Broken Eye — Brent Weeks

As the old gods awaken and satrapies splinter, the Chromeria races to find the only man who can still end a civil war before it engulfs the known world. But Gavin Guile has been captured by an old enemy and enslaved on a pirate galley. Worse still, Gavin has lost more than his powers as Prism--he can't use magic at all.

Without the protection of his father, Kip Guile will face a master of shadows as his grandfather moves to choose a new Prism and put himself in power. With Teia and Karris, Kip will have to use all his wits to survive a secret war between noble houses, religious factions, rebels, and an ascendant order of hidden assassins called The Broken Eye.