Man, I feel like I've been doing this forever; I wonder what level I'm at... *Checks the little number at the top right* Oh... only level 9... alright...
Tip: At level 80(the final level), the boss spawns 3 minions, and then attacks you himself. It may help to prepare a lot of potions beforehand, since the boss is pretty tough. Personally, I used over 60 different potions (some were transmuted in earlier runs), which may have been overkill, but it worked!