Alarum

Read the target clause carefully and the design intent jumps out: this pump spell refuses to touch attackers. The +1/+3 split puts toughness first and power second, marking it as a defensive tool rather than a growth spell, but the untap rider is where the real trick lives. It only pays off when the target is already tapped, which sets up a two-turn sequence: a vigilance-less creature swings on your turn and stays tapped, then on the opponent's turn this readies it back up at instant speed so it can declare a block. The same body gets to attack and defend in a single round of combat, which is precisely what tapping-to-attack is supposed to forbid. The targeting restriction reads less like a clean balance lever than like a designer drawing a boundary, a way of saying "this is not Giant Growth and was never meant to grow your swing." It is a fiddly piece from an era when instants reaching into the untap step had not been fully mapped, and the constraint is the entire identity: it can only buy back the attacker you already spent, never make a new threat bigger.