Hi! I just found out about this game thru Game Maker's Toolkit, and I loved it!
I did run into a crash during the boss fight with the mushroom tho. I used my cleared puzzles to bombard the boss and the summons. I killed the boss just as they were summoning the second summon, and then I killed the first summon and second summon in the next two turns. The game crashed at this point.
Thank you for making this wonderful game! I'm sad that the game crashed, but I hope to see it fixed in the future!