Mushroom Pit

{t} : Add {c} to your mana pool.

Whenever a creature token is put into your graveyard from play, put a charge counter on Mushroom Pit.
{t}, remove a charge counter from Mushroom Pit : Add 1
mana of any color to your mana pool.

{t}, sacrifices Mushroom Pit : Create X 1/1 green saproling creatures token where X is the number of creature tokens you control. Activate only if Mushroom Pit has 10 or more charge counters on it.