Loki's Scepter

Threaten effects have always paid for themselves with impermanence: you borrow a creature, swing, and hand it back at cleanup, so the ceiling is one turn of tempo. What separates this from a single-use Act of Treason is that the theft rides on a permanent that keeps working after the borrowed creature goes home. The enters trigger does the familiar act (steal, untap, haste, stamp a temporary Villain type), but the artifact stays behind as a color-fixing mana rock. That reframes the cost entirely. A one-shot steal spell wants to convert immediately or it rots into a dead card; here the theft is essentially free upside bolted to a permanent you would run for its ramp alone. The Villain rider rewards a closer look: temporarily marking a creature with a type it did not have opens interactions with anything that keys off Villains, turning a stolen blocker or utility body into a tribal trigger for the turn you control it. And because control expires at cleanup, the standard sacrifice-outlet line applies (grab the creature, feed it to something that eats it, and it never returns), which the artifact's survival makes cleaner since the mana source persists regardless of what happens to the borrowed body. It is a quiet answer to the obsolescence problem that dogs threaten effects: staple the steal to something that earns its slot after the steal has already resolved.