Isochron Scepter

The imprint mechanic shows up on a handful of artifacts as a one-shot, a single use baked into a permanent. Here it becomes an engine. Lock away any cheap instant and the artifact reprints it every turn, untapping in your untap step, ready to fire again for an activation cost and a tap. That repetition is what makes the whole thing tick: a single counterspell becomes a permanent tax on the opponent's stack; a Lightning Bolt becomes a clock that never leaves the battlefield. The mana-value-2-or-less clause is the real governor on the design, holding the pool to cheap, efficient instants and keeping the splashier spells out of reach. Two more restrictions shape how it plays. The copy is cast without paying its mana cost, so additional costs and alternate costs (the spell still has to be legal to cast) dictate what is worth imprinting; and the exiled card is gone if the Scepter dies, which turns artifact removal into a two-for-one. The degenerate corner found fast: imprint a free-to-resolve lock like Silence and opponents simply stop casting spells, or pair it with cantrips and bounce to grind incrementally forever. It is a build-around in the truest sense, a colorless shell that asks you to bring the instant and then rewards you for bringing one the opponent cannot easily answer. The artifact does almost nothing by itself and everything once loaded, and that tension is what has kept it in toolbox and prison decks for two decades.