Plague Rats

A creature whose power and toughness count copies of itself is, in 1993, a genuinely strange object: it scales linearly with redundancy in a way nothing else in the original set did. When the game had no deck-construction limits on nonbasic cards, that scaling was the whole pitch: stack a deck with as many Plague Rats as you could draw, fill the rest with Swamps, and mulligan toward the swarm. Two rats are a 2/2 for three mana; four are a 4/4; the math only matters when the deck is built to find them all. The design is the ancestor of every "lord of itself" effect that followed: Relentless Rats, Shadowborn Apostle, and Rat Colony each carry the explicit "a deck can have any number" clause that lets them finish what this card started. The original never got that clause, which is exactly why the four-copy rule (introduced after Magic's first tournament season) quietly defanged it: capped at four copies per deck, the swarm rarely grows past a 4/4, and the build-around stops being a build-around. The card freezes a moment when Magic was still working out what its own rules meant: if power and toughness can reference the board, what other countables are fair game? The answer turned out to be nearly all of them, and Plague Rats got there first, before the design space it opened had a name.