Original title: ダンジョン オブ レガリアス ～背徳の都イシュガリア～
The floating city of Windal was full of prosperity due to its advanced magic culture. However, an unexplained massive magic explosion sent the city crashing to the ground, killing almost all of its citizens. Only a huge crater and the ruins of the city underneath it remained.
Nomads built many villages and over time, the area turned into the large metropolis Ishgalia. Reckless adventurers came to the city to challenge the demon-infested labyrinths under the city in the hopes of striking it rich. The battle-seasoned Orias, who has no memories before becoming a mercenary, arrived at Ishgalia in search of his forgotten past. What awaits him in the depths of the labyrinth and the ruins of the floating city?