Black Goat of the Woods

Delve (Each card you exile from your graveyard
while casting this spell pays for {1})
Whenever you mill a creature card, add {b} or {g} to your mana pool.
If you would draw your second card each turn,
you may instead mill X, where X is the number
of creature cards in your graveyard. If you do,
return a creature card from your graveyard to
your hand.