Maximum Mountain (マキシマム
When modern Duel Disks were created, many prototype Duel Disks were abandoned in the mine. Through unknown circumstances, R0, the Mutsuba-style Mobile Duel Device, was also abandoned in a laboratory that was sealed off from the rest of the mine and knowledge of its presence was hinted at in a book in the Goha #6 Elementary library, but was hidden from the Mutsuba family.
When Asana Mutsuba made the decision to Duel Yuga Ohdo and crush Rush Dueling, she decided to use a Maximum Monster against him. Knowing that the previous two Maximum Monsters had been created by rewriting Duel ID cards, she had the Heavy Cavalry Duel Club excavate several Duel Disks from the mine in the hopes that they would find three cards stable enough to be rewritten; eventually succeeding in creating "Wyrm Excavator the Heavy Cavalry Draco", an event witnessed by Goha #5 Elementary's Space Operations Duel Squadron.
Yuga learned of the mine and R0 while researching in Goha #6 Elementary's library and tricked Asana into sending him, Luke, Romin Kassidy, Gavin Sogetsu, Seatbastian, Kaizo, Rayne and Rino to the Abandoned Dorm. From there they escaped into the mine after Yuga sent Kaizo and Seatbastian to ask Nail Saionji about the mine and if he could borrow Nail's own Maximum Monster; "Yggdrago the Sky Emperor". Nail sent Kaizo back with Tracker to assist them in finding the mine, which they eventually reached, uncovering several prototype Duel Disks for Yuga to recreate "Supreme Machine Magnum Overlord". Asana and the Heavy Cavalry Duel Club arrived soon after and they Dueled a second time, during which "Wyrm Excavator" and "Magnum Overlord" clashed, disintegrating both sets of Maximum cards from the strain, while also exposing the mine to the air due to the energy emitted by the Solid Vision. Yuga eventually defeated Asana and found R0 for her, bringing the Heavy Cavalry Duel Club to accept the idea of modification.
Following Yuga and Asana's second Duel, Hunt returned to the mine hoping to excavate all the Duel Disks and sell the ID cards after converting them into Maximum Monsters. He was discovered there by Goha 66, who made a deal with Hunt to help him excavate the Duel Disks, remaining at the mine after he and Hunt stripped the mine almost completely of Duel Disks. Other parties who had heard of the mine soon set their sights on it hoping to gain Maximum Monsters of their own; Luke brought Hunt to the Abandoned Dorm to ask Asana's permission to dig there, unaware of Hunt's actions, while Braun Honya challenged Asana to a Rush Duel for the right to dig in the mine; Asana settled the matter by having Braun and Luke Duel one another. After the Duel, Luke allowed Braun and his friends to dig in the mine with him, Hunt, Romin and Gavin, though as Hunt had already stripped the place, only Asana found a Duel Disk, which she extracted the Duel ID card from to give to Yuga at the Goha Rush Duel Team Battle Royal.
- Yu-Gi-Oh! SEVENS episode 03939: "Reclaim Mutsuba's Pride!"
- Yu-Gi-Oh! SEVENS episode 03838: "Unearth the Maximum!"
- Yu-Gi-Oh! SEVENS episode 04242: "Space Operations Duel Squadron"
- Yu-Gi-Oh! SEVENS episode 03333: "Goha #6 Elementary School"
- Yu-Gi-Oh! SEVENS episode 03434: "The Shiatsu Nether-Empire Strikes Back"
- Yu-Gi-Oh! SEVENS episode 03535: "Sound! Gohanium"
- Yu-Gi-Oh! SEVENS episode 04545: "Upstart Hunter"
- Yu-Gi-Oh! SEVENS episode 04343: "Opening! Team Battle Royal"