After you rescue Buckbeak, you must fight Professor Lupin when he turns into a werewolf. First, use Fumos with Hermione if she goes first. Fumos will cover Buckbeak and raise his ability to dodge attacks. To ensure that Hermione goes first, you should either equip her with the best items to make her agility the highest, or just make sure she is the highest level person and the only one with items equipped. Lupin only attacks Buckbeak. This battle is rigged so that Buckbeak always goes first, then Lupin, then yourself. Buckbeak will attack Lupin every turn, doing about 20 to 25 damage. Lupin has about 600 HP. None of your spells affect him -- this battle will rely on Buckbeak. If he dies you will lose. The only thing you can really do is use Fumos to protect Buckbeak and keep using potions on him when he gets hurt. You can also use the card combo Cracker Jinx. It does about 40 damage to Lupin.