Final Fantasy VI HD Walkthrough Part 130: The Depths of ZoneEater Part 1

In the South Eastern seas is an island shaped like a triangle. It is here that you will find your last team member and some cool items. First though you have to get eaten. No joke. Get into a fight with ZoneEater, a monster that roams the island, and let him suck you in. In doing so you are somehow transported into the island where you can get at all of the treasure. I am not sure if you can kill the monster, I did not try it after getting out of the caverns below.