"Tethermage's Advantage"

A one-mana +2/+2 can win combat or create a surprise block, but it provides no lasting card advantage and reach is matchup-specific.

Could be wrong if Prepared or other unrevealed green synergy could reward cheap targeting or untapping more than the revealed context suggests.

The efficient Pioneer field gives little room to a creature-only combat trick that neither protects from removal nor advances a proactive plan alone.

Could be wrong if A creature deck may value the untap as a compact tactical effect rather than merely a pump spell.

Even Creature Toolbox would need a specific untap payoff; +2/+2 and reach alone are far below Modern's usual rate for a card.

Could be wrong if A presently underrepresented creature-combo shell could make the untap clause materially more valuable.

Legacy demands unusually efficient, resilient interaction or a powerful engine; this is generally just a narrow one-shot combat exchange.

Could be wrong if A specialized tapped-creature combo could use the untap clause in a way ordinary combat decks cannot.

Elves can use the surprise untap, pump, and occasional anti-flying block, but a card-neutral combat trick is unlikely to earn many slots.

Could be wrong if Pauper's creature matchups may make the low-cost blowout and reach mode more useful than expected.

It is a cheap, flexible way to reuse a tapped creature and win combat, but affects only one creature for one turn and is highly replaceable.

Could be wrong if A commander or unrevealed payoff that rewards repeated untapping could make this a stronger niche inclusion.

A one-mana +2/+2 trick can reverse combat, untap an attacker into a blocker, and occasionally punish flyers; it is useful but card-neutral.

Could be wrong if Unknown speed, removal, and archetypes determine whether holding up a combat trick is worthwhile.