Planeswalker Symbol (MB1) 

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. 

Steve Luke