Rivanna, Goddess of the Veil

Rivanna's power and toughness are each equal to
the number of cards in your graveyard and exile.
As long as Rivanna is in your graveyard and you
control a Swamp, your black creature spells with
CMC 6 or less have delve if you pay 2 life when
you cast them.
You may play Rivanna from graveyard and exile.
If you do, sacrifice 2 nonland permanents when
you cast Rivanna.