Primal Infusion

Stockpile {g} (Exile this card from your hand: It gains "{g}: Put a cache counter on this card." and "You may cast this card from exile if it has a cache counter on it with its cost reduced by {1} for each cache counter on it.")
Untap target land. It becomes a 7/7 Elemental creature with haste until your next turn. If this spell was cast with no cache counters on it, it gains vigilance, reach, and trample until your next turn.