The only boss of the challenge is The Immovable, an animated armor with 457 health, 121 attack damage, Magical Attack and Retaliate: Fireball. In addition to these stats, whenever he is reduced to about 90% health, if there is a bloodpool on the map, he will turn the nearest bloodpool to acid, heal, and his attack damage will drop by about 10%.
The only strategy with which I have been even nearly successful is with a dwarf bloodmage. When I finally defeated him, it was because I got a lucky combination of an Orb of Zot and Midas Gloves before killing any enemies. I saved up using the Midas Gloves until I could purchase the Orb of Zot. I saved all the bloodpools I could and leveled up to level 8. Then I burned all my remaining mana potions and mana PISORFing the boss. Then I converted every excess item I could, and every glyph other than PISORF. I activated the Orb of Zot. Then I began hitting the boss, healing using bloodpools, and using PISORF on him whenever I had maximum mana. When I ran out of bloodpools, I killed any enemies that were weak enough to net me a health gain from their bloodpool, and then converted my PISORF and started using all my health potions. Even so, it took my last potion to be able to kill him.
Here is another strategy: Using gnome convet items to mana potions and PISORF beat the Boss. Don't leave any blood pools to the Boss! Drink health potion then Convet HP to MP by using BLUDTUPOWA (you can gain ONE mana without any uncovers).