Barbed-Back Wurm

The activated ability is hostile by design: it only works against green creatures, and only ones already committed to blocking this Wurm, so it does nothing on offense unless a green blocker steps in front. That narrow window is the whole point. Mirage was built around regional color tensions, and black was positioned as a predator on green, the color of fat ground creatures that would otherwise wall a 4/3 indefinitely. Paying repeatedly shrinks a green blocker until it dies, turning what should be a stalemate in green's favor into an attrition the black player wins. The shape of the ability also explains why it reads as so dated now: modern design almost never builds combat effects that key off a single opposing color, both because it dilutes the card against every other matchup and because color-pie hosing has largely migrated to spells and sideboard cards. As a body, a 4/3 for five was already unremarkable when it was printed; the value lived entirely in that color-locked grind. This is the design philosophy of a moment when a creature's job description could include "specifically beats green," and when that assignment was considered enough to justify the slot. The Wurm survives as a record of a time when color hatred was stapled directly to creatures rather than left to the players building decks around them.