You can destroy up to three target creatures. He only gets exiled if one of the creatures you choose to destroy is not attacking. If you destroyed 1 or 2 attacking creatures, he would stick the board. He would also stick the board if you destroyed no creatures. I would actually argue that this card is too powerful to print in standard. 5 mana instant speed destroy up to three target creatures is already really strong. Doomskar costs 5 mana and destroys all creatures, even your own, and it is sorcery speed. Devastating Mastery costs 6 to destroy all permanents, including your own, and is sorcery speed. With this card, you could theoretically at instant speed destroy 3 attacking creatures, block a 4th creature, and heal for 2, then have a 2/4 lifelink on the board, all for 5 mana. This is a joke card so I kept the rules simple. If this was a real card, I would add "For each creature destroyed in this manner, it's controller investigates" to bring it in line with cards like Fateful Absence. I would also have to seriously debate if it should be bumped up to costing 6 (3WWW), but maybe add first strike as well because 6 mana is really slow.