I was actually thinking maybe a character from Qaylu who was betrayed, banished and set adrift in a boat to slowly die only to wind up drifting into the Hamrock Isles by chance. Then he'd throw his lot and service in with Oromis in exchange for his life and the chance to see the traitors who destroyed him devastated in return. 

I'm not sure exactly what his skills would be, but either someone skilled with intrigue, social manipulation and assassination or maybe a strategist, scholar and tactician. In either case his own citadel's lord felt threatened by his competence and didn't believe someone of his abilities was content with remaining a servant and had them cast out to die of starvation and exposure at sea.