| This article is based on data from a Japanese-only game.|
The following content has not been released in the English language, so details are subject to change at any given time.
The Aqua Labyrinth can be accessed in a basement in Aquaveil after finding 15 stones scattered on the World Map. There are 25 levels in the dungeon, with the occasional mini-boss, usually Barbatos Goetia, who sometimes fights alongside Sabnock and Dantalion. When the bosses are defeated, they drop chests with powerful weapons. In the PlayStation Portable port of the game, one of these bosses is changed to Leon Magnus. When the player reaches the 25th floor, the boss, Magnadeus, will be waiting to fight the group. Once the player has defeated Magnadeus, Karyl Sheeden appears and speaks to the player.