This would be Levi's ultimate weapon against the Second-Circle Wizards before he advanced to the second-circle. If he worked with Levi, the two giant killing monsters would be enough to resist the Second-Circle Wizards.
The Corpse Digger's strength was naturally exchanged for its high cost of manufacturing and fuel. The energy consumed by this huge creature that weighed dozens of tons fighting with all its might was far from what a lightweight alchemical creature like the Swordsman Mantis could compare to. It might consume hundreds of Aether Stones in a battle. This was undoubtedly burning money.
But now, there was Ace. As long as Levi let Ace fill the underground fire under the Black Fire Island with fire elemental power in advance, he could use Ace as a "mobile power source". When Ace was fighting, he could integrate into the undead digger's activation furnace and replace the burning of the Aether Stone to produce energy.