Mulch, the Risen Compost

As long as you have less then eight cards in your graveyard, Mulch isn't a creature.
Mulch's power and toughness are each equal to
the number of card in your graveyard.
{t}, mill 2: add {b}{b}{g}{g}.
Whenever a card is put into your graveyard, you
may pay {b}{g}. If you do, create a 1/1 white
Spirit creature token with flying.