Balrog

Evolved Balrog
Evolved Balrog comes in two different forms depending on whether you defeated it before or not. It replaces the D3 boss of the volcano if your volcano team contains the pet Balrog. It is stronger than the normal D3-10 boss in volcano. The first evolved Balrog you fight is stronger, has 1 million HP initially, and retains HP damage between fights so you can kill it slowly over multiple encounters. Subsequent Evolved Balrogs you fight will have 200k HP and it will not be retained between different dungeon instances.

Evolved Balrog has a massive self heal that can be prevented if your party contains the pet Wizard in it, making it effectively mandatory. Also bringing in shiny stone and magic ore will weaken the evolved Balrog, with the shiny stone also reducing its chance to use multi-target attacks. The reward for beating the first evolved Balrog is allowing you to evolve your own pet Balrog. The reward for subsequent victories is that it drops Balrog Horn. The pet Balrog gets additional HP which scales linearly with the number of Balrog Horns you own

Farming Horns of Balrog
For efficient farming, have as many rogues on your team as possible. A sample Wizardless farming team is:
 * Elephant with neutral gear and Earth/Water gems
 * Black Hole Chan with fire gear and 1-2 Water gems
 * Santa with fire gear and 1-2 Water gems
 * Balrog-Rogue (Balrogue) or Balrog-Mage with neutral gear, water gems, and knives
 * Two rogues, possibly Book-Rogue/Nothing-Rogue to catch the Blacksmith event, with knives
 * DL in the 160-180 range; CL in the upper 30s to mid 40s; all maxed and max enchant T3 gear

(If you need Wizard, replace one of the rogues with Wizard)

As of Aug 2021, Balrog Horns have a softcap of 900, making the Balrogue strategy makes less useful - it may be worth it to evo Balrog into a mage to begin with and let it take a little longer to get to 900 horns.