Altar of Demeter

(Altar of Demeter is green.)
Whenever a land enters the battlefield under your control you may add one mana of any color the
land can produce to your mana pool. If you do
put a devotion counter on Altar of Demeter.
At the beginning of your end step if Altar of
Demeter has 4 devotion counters on it you may
pay {2} if you do exile Altar of Demeter, then
return it to the battlefield transformed under
your control.