In the Depths, you follow the statues to the Great Abandoned Central Mine, where you must defeat Master Kohga in battle.

Master Kohga: Truck

You can't grab onto his vehicle with Ultrahand. Instead, you can either knock him off by shooting him with arrows or throwing weapons at him, or you can try to lure him into driving the vehicle toward you, then sidestep it and jump onto it. Don't try to take control of the vehicle, because Kohga will soon make it disappear. Instead, just hit him repeatedly until he disappears.

He will keep summoning new vehicles, including some that have barriers to make it more difficult to knock him off. Later, he makes a rocket-powered vehicle, but you can just sidestep it and it will crash into the wall, stunning Kohga and allowing you to run onto the vehicle, where you can hit him repeatedly.

After the battle, open the chest that appears, and you will get a Huge Crystallized Charge, worth 100 Crystallized Charges. This will allow you to go to a crystal refinery, such as the one north of Lookout Landing, to increase your Energy Cell capacity.

Master Kohga will be added to the Character Profiles. This begins the side adventure Master Kohga of the Yiga Clan.