Edge of Darkness - The Darkness & Light Series, #3

"Such power as this cannot be altered from its true form. It is Darkness, and it will consume him. You will not recognize the man he becomes..."The threat that has followed on Bolin's heels like a dog after scraps is growing. To fight it, Bolin must put aside his pride and, for once, rely on the strength of others. All of which he must do while battling a growing madness and without Ciara at his side.
For her part, Ciara is trying desperately to set things right, but finds to do so means placing her trust in the unlikeliest of allies. When Donovan seeks her out, his insistence they need to work together forces Ciara to look beyond her desire for justice. Darkness has woken and looks to claim all it once possessed. To do so, however, it will need to turn the empire's most dangerous weapon to its side.
If Darkness succeeds, not even the Goddess herself will be able to prevent the outcome.