Mogg Sentry

The trick is that your opponent supplies the math. Left alone, this is a 1/1 Goblin that trades with a token and nothing else; the moment an opponent fires off a spell, it swells to a 3/3 until end of turn, and a second spell in the same window takes it to 5/5 or higher. That makes it a punisher: a body that taxes the reactive player for the crime of holding up countermagic, chaining cantrips, or trying to remove your board mid-combat. The design wrinkle worth noting is the timing. The buff fires on cast, while the spell still sits on the stack, before it resolves, and it lingers only until the end of the turn it triggered. So the trigger and the attack step do not naturally line up: a control opponent does most of their interacting at instant speed during your turn, which means casting removal during your attack pumps the very creature swinging at them, while a counterspell cast on their own turn grows a goblin that is sitting at home with no one to hit. The opponent controls the dial completely, of course, which is the whole point: every interactive spell they want to cast also feeds the clock. The cleanest way to neutralize it is simply to stop casting, and against an aggressive red deck that is rarely a posture the reactive player can afford to hold.