Is just beyond hard.
There are four mini-bosses. Fine. The room with the fireballs rolling. Fine. Staying in the fire cages with constantly spawning creeps. Fine.
Final boss. Not fine. Ungodly freaking difficult.
I get the concept. And I get that its beatable. But it is just way too much to warrant the amount of time it takes.
If you want to put something into the game that is just the most difficult thing you could fathom, then fine. Give it a better reward.