The List

Ertai's Meddling

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.

Tempest

When target spell is successfully cast, put X delay counters on it. X cannot be 0.
During each upkeep of that spell's caster, remove a delay counter from the spell. If the spell has no delay counters on it, it resolves.