From amazon.com:

The nail-biting continuation of the Lightbringer series from New York Times best seller Brent Weeks.

When does an empire fall?

The Seven Satrapies have collapsed into four - and those are falling before the White King's armies.

Gavin Guile, ex-emperor, ex-Prism, ex-galley slave, formerly the one man who might have averted war, is now lost, broken, and trapped in a prison crafted by his own hands to hold a great magical genius. But Gavin has no magic at all. Worse, in this prison Gavin may not be alone.

Kip Guile will make a last desperate attempt to stop the White King's growing horde. Karris White attempts to knit together an empire falling apart, helped only by her murderous and possibly treasonous father-in-law, Andross Guile.

Meanwhile Teia's new talents will find a darker use - and the cost might be too much to bear. Together they will fight to prevent a tainted empire from becoming something even worse.