Autumn Wraith

Vigilance
Whenever another nontoken creature you control
dies, you may pay {b/g}{b/g}. If you do, create a 2/2
black and green Treefolk Spirit creature token.
{4}{b/g}{b/g}, Sacrifice Autumn Wraith: Create X 2/2
black and green Treefolk Spirit creature tokens,
where X is the number of creature cards in your graveyard.