In the World Of Ruin, go to the northeast triangle island. Bring strong characters. There you will meet a monster named Zoneeater. It uses Demi, but also uses an attack called "Engulf" that sucks a character into him. Allow him to use "Engulf" on all of your characters. The game will not end. Instead, you will end up in a cave. This cave has strong monsters and great treasures, such as the Genji Armor. Jump across the bridges and avoid the walking people to eventually reach the end. Walk through the door and you will see a covered-up person. Talk to him and he will join your party.