Triton’s Shell of the Tides Quest Walkthrough
Start She Who Controls the Seas to get more maps.
Go to Makedonia and head to the Underwater Cavern. A few enemies have set up a camp inside of that location. Find the treasure chest. The item you are looking for is inside of it.
The chest is at the back of the camp. Collect the items and go back to Xenia to complete this quest.