Aim High

The untap clause is the whole reason this exists at instant speed: point it at a creature that already attacked, or one that tapped for an activated ability, and it springs back upright with +2/+2 and reach, ready to ambush a swing-back as a fresh blocker. The reach rider folds the typical fight against fliers into the same card, so a ground creature can suddenly police air it had no business reaching. The design lives in the gap between two pieces of green's toolkit that usually arrive separately: the pump spell that wins one combat, and the vigilance-style trick that lets a creature do double duty. Stapling untap onto a combat trick manufactures something like vigilance after the fact, on demand, which is a far more deceptive blowout than a static keyword the opponent can see coming when planning an attack. Flexibility is what it charges for, and the bill comes due before the spell ever finds a target: you need a creature already worth pointing it at, and a +2/+2 swing rewards a body with relevant abilities or a board already trading well rather than one fragile bomb. Cheap and narrow, built for the player who wants the same creature to attack and then stand guard inside a single turn.