Ertai's Meddling [Tempest]

Set: Tempest Type: Instant Rarity: Rare Cost: {X}{U} 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.