Errantry

The +3/+0 reads cheap until you reach the second clause, where the price is collected: enchant something and only that creature swings the turn you want the bonus to land. The whole board sits at home so a single attacker can hit for three more, which inverts the usual logic of a power-only Aura. A flat boost to power turns a creature into a clock, and the "attack alone" restriction is the brake that keeps that clock from being free, funneling all your pressure into one target the defender gets to plan around. The card rewards a deck built on a single threat and actively punishes the go-wide plans where a generic pump would be strongest. That makes it best on something already evasive or hard to block, where one creature getting through matters more than five getting chumped: the restriction stops mattering once nobody else was going to connect anyway. This is honest early-design about red's aggressive bonuses arriving chaperoned, a leash bolted onto the boost so the color gained reach without simply handing aggressive decks a free upgrade. The number on the card is generous; the clause underneath it is doing all the shaping.