Thieves Of The Blood

Description for THIEVES OF THE BLOOD by Tim Waggoner:

Discover the dark world of Eberron as one assassin-turned-cleric searches for peace in a land that knows only blood
 
Diran Bastiaan was once one of the most feared assassins in the land—one of the best money could buy. But after a life-altering spiritual experience, he has turned his back on murder, seeking the life of a wandering priest of the Silver Flame. All he wants is peace. But in a rough port town on the edge of the world, his past is about to catch up to him—and killing may be his only hope.
 
When raiders known as the Black Fleet hit the town, capturing Diran's former lover, he must risk everything to save her. Accompanied by a half-orc fighter named Ghaji, he races against the clock, knowing time is quickly running out. For these are no ordinary pirates bent on plunder, but minions of Erdis Cai, a warlord and servant of the Blood of Vol.

This is #1 in Blade Of The Flame Series.