Riverguard's Reflexes

Most white combat tricks that hand +2/+2 and first strike stop there, and they read as pure ambush: cast, win the exchange, done. The third line here changes the geometry. Untapping the target on resolution means an attacker resolves combat and then stands back up untapped, ready to block on the crackback, so a single body defends the turn after it attacked. On the opponent's turn, it conjures a blocker from a tapped-out board, punishing an attack the opponent committed to on the read that you had nothing. The pump and the keyword do the immediate work: the boost wins most exchanges outright, and first strike lets the target kill what it meets before absorbing damage. But the untap is why the spell is priced to want the latest possible window, after attackers or blockers are declared and the combat math is locked in, at which point this instant rewrites it and leaves you a live blocker besides. It rewards holding two mana and knowing exactly which combat step will cost the opponent the most.