Jungle Wurm

A 5/5 body for five mana with a clause that only the defender can pull: that inversion is the whole design. The penalty triggers off being multi-blocked, so the more creatures stand in front of the Wurm, the smaller it gets. A single blocker and the Wurm swings at full power, trading up or eating the blocker whole; two blockers drop it to a 4/4 it can still survive; three blockers shrink it to a 3/3, low enough that the defender can kill it while losing less. So the card hands the blocking player a lever, and pulling it works in the defender's favor: gang-blocking is exactly how you neutralize this thing on the cheap, because each extra body subtracts from the attacker rather than adding risk to the block. That makes the Wurm a roadblock-breaker only against light defense; into a developed board it asks the attacking player to clear the way first or accept an unfavorable swing. It is honest, self-limiting design from an era when vanilla green fatties set the curve and the experiment was figuring out what to bolt onto a big body. Here the bolt-on is a built-in drawback rather than an upside, a penalty that scales with the opponent's blockers, which is why the Wurm reads as a fair creature rather than a menacing one.