Devoted Druid

The combo player's mana dork. A standard untapper charges its toll in mana or cards; this one pays in vitality, weakening its own toughness with every untap. That tradeoff makes it a finite engine: tap for green, untap by branding itself, repeat until the body collapses, netting a green for each cycle you can survive. Left alone it produces a handful of mana before killing itself, which is fine but unremarkable. The detail that built an archetype is that the untap ability has no mana cost and no once-per-turn limit, so anything that erases or prevents the counters breaks the loop wide open. Pair it with an effect that holds the toughness stable (Vizier of Remedies cancels the shrinkage outright) and the math stops being finite: infinite untaps, infinite green mana, and any mana sink in the deck becomes a kill. That interaction made it a fixture of dedicated combo decks for years and a recurring name on watchlists, all from a 0/2 that does nothing dangerous on its own. The design is honest about its cost, and that honesty is the trap: the self-mutilation reads like a brake, until you find the card that disconnects it.