Walkthrough may be a bit of an overstatement, but here is how I beat it.

Firstly, make sure that you have collected at least 15 pieces of art, and given the 3 items that give poison immunity to some people you will be taking

Secondly, only take combat troops - a swarm of grunts is best, maybe some animal hunters if that's your fighting style, they do alright in this fight. Lumberacks if you absolutely have no other option. Farmers, children, carefrees are out of the question

Now, onto the fight itself, and it is a very tough one. The most important thing is to take your time. If you just throw your guys at it and wait for one side to be victorious, it shant be you. Watch his attacks until you have memorised what each looks like. When he is underground you must keep moving and must NOT backtrack, because then he will surface and kill you. Move in wide circles, where possible. His other move if memory serves is to spin at you, which he does for a while before getting exhausted, and then you should strike - throw a bunch of grunts at him, and call them back well before you think he's going to attack. Rinse and repeat

gl

- Scottie