It was created by the legendary Magician, Velvet to store the treasure's he's accumulated in life. The Dungeon was managed by Returner, a Carbuncle, and defended by Skeletons and Greater Skeletons. Spirit Stones of all attributes were abundant here, due to Velvet's influence.
Returner was severely injured by some Human adventurers who invaded the place for the treasure. After being discovered by Gobue, who brought the Carbuncle to Ogarou, it offered the Dungeon's treasure to him if they drove away the Humans. Rou agreed, and after killing the adventurers took everything the Dungeon had to offer. After sealing of the main entrance, E then expanded the Dungeon while mining for Spirit Stones, and it became an extension of Parabellum's headquarters.