Aremag was a dragon turtle who protected Port Nyanzaru in exchange for treasure. The Wafflecrew ran into difficulties paying him, and tossed their Halruaan Force Bomb in Aremag's mouth.  The dragon turtle was killed by the massive explosion and his body parts flew high in the air, raining back down into the sea. 
The mouth of the Bay of Chult is watched over by Aremag, a dragon turtle with a blind, milky left eye and a piece of its shell missing. Aremag demands that ships toss treasure into the bay to appease it. Aremag then gathers up the loot and hides it in its lair, which no one yet has found.