Tiraath, Eternal Forest

Indestructible
You must pay this card's mana cost to cast it as a land. This does not count as your land per turn.
{t}: Add {g}{g} to your mana pool.
Leftover mana in your mana pool at the end of phases instead remains as green mana in the form of forest counters on forests you control. Each forest with a forest counter on it has: {t}, Remove a forest counter from this card: Add {g}{g} to your mana pool.
This card can be your commander.