I liked this a lot! It's a great demo to a game. I don't have much in the way of encountering bugs but I do have suggestions!
1: I feel like the thief archetype is one note sometimes, so I had an idea. Gigantification or Titan potion, for thieves with only darker clothing and/or adventurers with no weapons (staffs do not count). If something needs to be sneaky, what better than to make them a bigger target! You could just increase the image size by a lot, but a crouching position would be fun.
2: Rapunzel potion would be funny. Lots of hair. Adventurers with a ranged weapon would have a hard time aiming with no sight!
3: I feel like there could be transformation potions, like an orc potion or a slime potion. Faster recruitment for the dungeon I guess.
4: Finally, conversion potions. Some who like to perform hurtful acts would be given a "no morals" potion which would turn them evil, with red eyes and a smirk.