Join Forces

The untap clause is the whole reason this reads as an ambush rather than a plain pump spell. Most white combat boosts operate on your own turn, sizing up attackers before or during the declare step; being able to untap up to two creatures at instant speed lets tapped-out attackers stand back up as surprise blockers, or lets a creature that already swung come home ready to trade. Splitting the +2/+2 across two bodies rather than piling it on one is the trade the design makes: board-wide reach instead of a single lethal swing, which suits it to go-wide strategies looking to break a stalled ground rather than overload one attacker. Where the untap earns extra value is with creatures whose abilities cost a tap, since restoring two of them mid-combat can free up a second activation the opponent was not counting on. What keeps it honest is that both halves cost whether you find one target or two: there is no discount for going small, so the card wants a real board before it is worth casting. Read as a defensive tempo play more than a racing tool, it rewards leaving mana open on the opponent's turn, where the untap-and-boost combination can turn an expected profitable attack into a blowout.