Iona's Blessing

Most creature Auras buff a body and hope it survives; the interesting clause here is the one that reads off the opponent's board rather than yours. The +2/+2 and vigilance make the enchanted creature a genuine attacker, but the ability to block an additional creature each combat is what changes the question the Aura answers. Against a lone attacker it does nothing beyond the stat bump; against a wide aggressive board it turns a single body into a two-lane wall, one creature soaking up two attacks. Vigilance is what lets the same creature carry both jobs across a turn cycle: it swings on your turn without tapping, so it is still upright and available to make those double blocks when the attack comes back at you. Offense and defense stack onto one card by design, and the two halves reinforce each other. The cost is the standard fragility of any creature Aura: a single removal spell erases the four-mana investment and usually the creature underneath, leaving you down both a card and a body. White has long leaned on enchantments to make one creature outperform its slot, but the usual move is subtraction (Pacifism switches an attacker off entirely). This does something structurally different: it packages the extra-blocking logic normally built into a creature's own text and straps it onto whatever is still standing.