Drenner was a male otter. He was the father of Norgle. He and his son were captured and enslaved by Vilu Daskar to work on Daskar's slaving ship, Goreleech.
Drenner died because he wasn't strong enough to hoist a log halfway up the Goreleech's mast, a sick joke the slavers played with the weaker and sicker slaves.
The joke involved giving slaves their "freedom" by having them walk the plank in the middle of the sea.
After Drenner died, Luke the Warrior took his place in the galley.