There needs to be a spell that just destroys whatever bubble is on the duel circle, and returns everything to normal.
Right now, if you're life or death or balance, you tend not to want to cast your school's bubble until you need to because it 1) lets the other player heal, 2) makes it so you can't heal, or 3) costs too many pips. But if you want to stop the other side from having damage boosts, what are you supposed to do? A spell that just gets rid of any bubble would be ideal.
