Map: Death Mountain
Recommended Element: Water
Heart Container: Sheik
Heart Piece: Impa
Skulltula: Defeat 1,000 enemies
The Goron forces will launch a boulder attack on the allied base. Fight your way through either the West or East Keeps, kill the Deku Babas then evade the rolling boulders uphill towards the East or West Boulder Keeps. Capturing the East Boulder Keep will reveal a red chest containing a Sealed Weapon.
Make your way to the other Boulder Bridge and capture it as well. After capturing the two Keeps, clear any nearby outposts and kill the enemies. Darunia will make his way to the allied base. Intercept him and engage him in battle. You can attack aggressively; just remember to be ready to dodge when he blocks your attack or he doesn't stagger. His Weak Point is revealed after his every attack. Darunia's attacks are slow and predictable so defeating him shouldn't be that much of a trouble. Once you defeat him, he'll fall back to the chief's room.
After that, massive Goron forces will swarm your allied bases. Do your best to defend them and defeat as many as you can. After a while, Darunia will regain his strength and march out again towards your bases. He'll attack the West Boulder Keep next.
Note: There's a fake stone wall that you can destroy, northeast of the E. Boulder Keep. Inside lies a chest and a Cuckoo. This one summons a gold cuckoo when attacked.
Defeat Darunia again and defend the W. Boulder Keep until Impa arrives. If she doesn't seem to move, make sure to head there and take out the Deku Baba blocking her path. Once Impa reaches the Boulder Keep, she'll launch a boulder attack on the Chief's room. The impact from the boulder will destroy the base entrace. This will prevent Darunia from recovering his stamina quickly and heading back again. Head inside and take out more Goron strongholds. The full strength of the Goron army will march towards the allied base. Use this chance to stop them and kill as many gorons as you can.
Shortly after, Goron Bombchus and their operators will make their way towards your keeps. Intercept them and defeat the operators to seize the bombchus and use them to bomb the Chief's room instead. Aside from bombchus and operators, you have to watch out for another goron detachment led by three captains. Take them out then proceed in assaulting the chief's room.
Once you're ready to fight Darunia, it will be better to lure the twp Big Poes and defeat them before facing him to decrease his power. Once done, use the same attack patterns to take out Darunia.
After the battle, Darunia will now be unlocked as a playable character.