Quilled Greatwurm

The self-sustaining feedback loop is the whole design: every point of combat damage a creature deals on your turn comes back as a permanent counter, so a board that connects grows faster each turn it survives. The wurm's own body starts the engine at 7/7, but the ability is anthemic, not personal: it fattens whatever you attack with, and because the trigger counts damage dealt to any target, not just to a player, even blocked creatures cash in as long as they live through the strike. A creature chump-blocked by something smaller still gets its counters. That growth is also the recursion fuel. The graveyard clause reads like a tax (an additional cost, layered on top of the six mana, that skims the equivalent of a full attack's worth of counters off your board), but in the deck this card wants, those counters are exactly what the anthem has been minting all game. You are cashing in a surplus the card generated while it was alive, and the "removing six counters from among creatures you control" phrasing means the whole board chips in, not one overburdened attacker. The survival rider is the only real brake on the ratchet: kill a creature in the damage step and its counters never land, so the payoff rewards a board resilient enough to trade and keep its bodies rather than one that empties on a single alpha strike. Green has always been the counter-accumulating color; here the accumulation is finally something you can spend, and the recursion closes the circle.