I'm not sure if this is the right place to ask, but I've noticed the boxes underneath enemies get filled when they are hit by certain types of spells. I've tried to figure out the matchups for each enemy, but I'm curious if meeting them does something. I managed to figure out the matches for the rat thief, but I didn't notice anything happen.
Ah! They're the weaknesses of the enemies. I might need to add an NPC that teaches you that.
lol. It's funny, immediately after I asked the question, I wondered if that had something to do with it. Regardless, I think it's a nice mechanic in the game, even if I didn't fully understand it at first. I think you're right though. I may just may have been blinded by how great and sexy the game is overall, but it wasn't readily obvious to me. An NPC or even a sign or note might help out the oblivious like me.