Dead Man's Bet — Gail Z. Martin

An errand turns deadly when slavers and vengeful ghosts capture Jonmarc and his friends. With the spirits and the slavers out to kill them, Jonmarc and a renegade soldier intend to get free or die trying to escape.

Soldier. Fight slave. Smuggler. Warrior. Brigand lord. If you've met Jonmarc Vahanian in the Chronicles of the Necromancer and
Fallen Kings Cycle books, you don't really know him until you take his journey.