Chapter 1, Mission 4
Enemy Hero: Oni the Brute
Enemy Level: 10
Enemy Items: Rusty Axe
- 0% Mastery: 17 Exp / 175 Gold
- 100% Mastery: 20 Exp / 210 Gold
- 200% Mastery: 24 Exp / 245 Gold
- 300% Mastery: 27 Exp / 280 Gold
As the hero and all his units are Fire element, using Water elemental units such as Shark Men is highly effective at winning quickly, whilst Wind units will be largely ineffective. If you don't have any Water units, Elite Dwarves are reasonably effective, though they will do damage very slowly to Oni.
Using a few items to start with more mana (like Staff of Holy Empire, use 3 or more for good results.), you can kill him quickly with goblins.