Gothwan Cooper is a thief working for the Nashers who turned against his previous allies after he was kidnapped by the Dead Rats for his knowledge of the location of the Crown of Neverwinter. The Nashers never attempted a rescue fearing it would leave them fighting on two sides. Your rescue of him during the quest The Dead Rats convinced him to turn over crucial evidence on the location of Karzov and the Crown of Neverwinter.