Corrupted Conscience

Mind Control was the template: take their best creature, make it yours. This pushes the trick one cruel step further by handing the stolen body infect, which means the creature you took is now killing its former owner in poison counters instead of damage. The math changes completely. Ten poison ends a game regardless of life total, so a single large attacker, properly directed, becomes a two- or three-turn clock that no amount of lifegain answers. Layered onto a control-magic effect, that turns a defensive steal into a finisher: you are not just denying the opponent a threat, you are converting it into the instrument of their loss. The five-mana price and Aura fragility (bounce the creature and the enchantment falls off; remove the creature and you are down a card) are the friction that keeps a permanent theft-plus-alternate-win-condition from being oppressive. What makes the design memorable is the symmetry of the cruelty: infect was built so the architects of corruption could spread it, and here the card literally corrupts an opponent's own resource into the disease. It is one of the few ways to bestow infect on a creature that did not start with it, which quietly opens combinations infect's home set never put on the same battlefield: enchant something with trample or doubled power and the poison total climbs faster than any toughness can absorb.