To unlock the Otka Island Maze you first need to obtain the Sol Blade from the Apollo Sanctum and then beat the game. After you beat the game and are prompted to save the gave, load it and sail from Tonfon to the west until you see a small island surrounded by rocks, wait until you see the whirlpool and sail right into it. You will end up on the other side of the rocks with the island. Land then go inside and then go to the door. Select it to initiate text then go to your inventory and use the Sol Blade. The Maze holds the Summon Catastrophe and extra boss Ancient Devil.
|Otka Island Maze||Obtain Sol Blade and beat the game.|