As an additional cost to cast this spell, behold a Merfolk (To behold a Merfolk, choose a Merfolk you control or reveal a Merfolk card from your hand.) and exile it. Whenever this creature enters or becomes tapped, tap up to one target creature and put a stun counter (If a permanent with a stun counter would become untapped, remove one from it instead.) on it. When this creature leaves the battlefield, return the exiled card to its owner's hand.