Ertai's Meddling

Mana cost: {X}{U}

Instant

X can't be 0. Target spell's controller exiles it with X delay counters on it. At the beginning of each of that player's upkeeps, if that card is exiled, remove a delay counter from it. If the card has no delay counters on it, the player puts it onto the stack as a copy of the original spell.