Setessan Oathsworn

The heroic mechanic always wanted a payload card, and this is the one that pushed the dial furthest among the green-bodied versions. Most heroic creatures earn a single counter or a one-shot bonus per trigger; here, every spell that points at the body lands two +1/+1 counters at once. The math is what makes it dangerous: a single one-mana protection spell or pump trick doubles as a four-point swing on toughness and power, and two cheap targeted spells in a turn can turn a fragile 1/1 into a five-power threat that nobody durdled to assemble. The body is the constraint that pays for the upside; a 1/1 dies to any reactive removal before the spell resolves, so the engine asks you to hold the trigger until you have both the target-spell and the mana to protect the investment. That tension (a payoff that demands you commit spells to a creature that wants those same spells to be Giant Growths or hexproof grants rather than card advantage) is the whole heroic puzzle in miniature, just with the reward turned up. It rewards a deck stacked with cheap targeted instants, and it punishes you for casting nothing the turn you play it. Counters, unlike the temporary buffs heroic often hands out, stick through the end step, which is the quiet reason this one closes games rather than just winning a single combat.