Guard Duty

Pacifism strips a creature's ability to attack while leaving it free to block; this Aura reaches the same destination by the opposite mechanism, handing the creature defender so the rules forbid the attack rather than a printed "can't." The practical result on the attack step is the same (the creature stays home), but the texture differs from hard removal: a creature with defender still trades in combat, still soaks an incoming swing, still serves whatever defensive plan its controller already wanted. That is why it never reads as a clean answer. What it shuts off cleanly is offense: a beater that has to attack to matter, an evasive threat in a race, a creature whose whole value was applied pressure. Against anything that wins by attacking, one white mana erases the clock; against anything that does its work standing still, it does almost nothing. The single-mana cost is the entire appeal, cheap enough to spend reactively without warping a curve, and the price of that price is the narrowness: it answers a specific problem rather than a general one. White has long made a family business of enchantment-based combat denial, from Pacifism through Arrest, each entry carving a slightly different slice of what a creature is allowed to do. This one takes the harshest slice for attackers and the most forgiving for everything else, which makes it an honest pacifier rather than removal pretending to be cheap.