The Thrall Captain is just a tougher version of another creature that serves Davy Jones in the Cursed Caverns, Kelpbrain. The only difference is that Kelpbrains use daggers and cutlasses instead of just cutlasses, yet wield a considerable amount of damage, while Thrall Captains can use all the sword skills (Sweep, Brawl, Taunt, and Blade Storm). Thrall Captains appear at Levels 43-50 and are found near two large pools of water (also called the Thrall Hall/Room for obvious reasons) in the Caverns on the East side along with the deadly Urchinfists (Levels 43 - 50, use grenades).