Exotic Terrain

Enchant land you control
Exotic Terrain enters the battlefield with two depletion counters on it.
Whenever enchanted land is tapped for mana,
add one mana of any of color to your mana pool for each depletion counter on Exotic Terrain, then remove a depletion counter from it. Then,
if Exotic Terrain has no depletion counters on it, transform it.