Feedback

An Aura that enchants an enchantment, then takes a point off its controller every upkeep: the design is a closed loop of the noun it cares about. The targeting restriction is the whole concept. As a clock, one damage a turn is a terrible rate, but Feedback is not a clock; it siphons life from the opponent's own investment in increments small enough that they often cannot justify breaking their own lock to stop it. It belongs to a lost design dialect where enchantments were the premium threat type and blue was handed narrow, oblique tools to interact with them sideways rather than head-on. The card sits inert until the opponent commits to a board built on permanents they cannot easily replace, and only then does it turn sharp against them. Wizards has not returned to "enchant an enchantment" as a serious template since the early sets; the modern game answers permanents by destroying or exiling them outright, not by parasitically draining their controller for committing to one. What remains is a working specimen of that older grammar, when a three-mana Aura that dealt one damage a turn under exactly one condition was a reasonable thing to print.