Night Soil

Oracle Text

1, Exile two creature cards from a single graveyard: Create a 1/1 green Saproling creature token.

Card Rulings

4/1/2008 A “creature card” is any card with the type creature, even if it has other types such as artifact, enchantment, or land. Older cards of type summon are also creature cards.
10/1/2008 The two creature cards are exiled as a cost. No one can respond to this. If no graveyard has two creature cards in it, the cost can’t be paid.