Gideon's Intervention

Naming a card and locking it out is one of the oldest white answers, but most of those effects stop at the spell: they prevent the cast and walk away. The second half is what makes this one strange. By also preventing damage from sources with the chosen name to you and your permanents, it reaches past the stack to whatever copy already resolved, but only along the damage axis. Point it at a burn spell and both the cast and the burn are dead; point it at a beater already on board and the attacks fizzle even though the creature stays. That distinction is the whole design tension: it is a hard lock on casting, but a partial answer to a permanent, since a named planeswalker still ticks up and a named creature still blocks, taps, and fires off any non-damage ability it has. Against a combo deck it functions as a hard lock on the one card the plan can't proceed without; against an aggressive deck it can read a hand and switch off the haymaker before it's cast. The cost of that reach is the choice itself: one name, declared as it enters, with no way to change targets afterward. It rewards knowing exactly what you're afraid of and punishes guessing wrong, which makes it a reactive tool that wants information before it commits. Sitting between the broad "you can't cast that" enchantments and the narrow single-target ones, it is more surgical than the former and more total, on casting at least, than the latter.