I really liked this game!
The art style was awesome, and the characters in particular looked great! The battles were fun and engaging, and it felt very much worth it to gather all of the upgrades before moving on to the final boss.
SPOILERS AHEAD FOR THOSE WHO HAVE NOT PLAYED:
My only real critique for the game is probably how the ending choice is made. If you choose to spare the boss, you die and lose the game. This would make sense, but the (green, I think?) monk has you answer a series of questions, all pointing you towards mercy.
I figured since these questions were set up in the side areas, it was a hint as to how to beat the boss (much like the invincibility charm). But when prompted with this in the final area, mercy just grants you a loss.
Other than that, I had a lot of fun with the game, and am happy to say I was able to make it that far!
Very well done, I'd be interested to see where you evolve this idea if you ever come back to it!