Backfire

Punishment-as-defense, encoded into a one-mana Aura. The design is a curio from an era when blue was still allowed to play in the damage-redirection sandbox that would later become red and white's territory: rather than counter the attacker or bounce it, you wire its damage back at its controller, turning the opponent's beater into a slow-burn liability. The structural trick is that the reflection scales with whatever you cannot block, which means the card rewards being unable to interact in combat (an inversion of how protection Auras usually read). The friction is equally instructive: it does nothing until the enchanted creature actually deals damage to you, the trigger fires on damage to you rather than on attack, and a single removal spell on the enchanted creature ends the relationship cleanly. You are also choosing the target, so the Aura's value depends on guessing which threat your opponent will commit to the red zone, a read that ages poorly the moment they draw a second one. It comes out of a short-lived design lane that treated combat as a contract the enchanter could renegotiate, punishing the attacker rather than stopping the attack, a lane modern blue has almost entirely vacated in favor of tempo and card selection.