Anima Dungeon One is a large underground facility near the Mass Driver Facility and Taura Melchior's house on Elru continent in the south east. After working their way through the convoluted layout of the facility Fei, Elly and Billy were able to find the Anima Relic stored in the deepest level of the facility. The Relic aligned with Billy and turned his Gear Renmazuo into the Omnigear El-Renmazuo. On the way out of the dungeon Billy was given an opportunity to test out his new Omnigear when the party was confronted by the Elements and their massive combiner-Gear the G-Elements.