Okestra, Swarm Vampire

Instants and Sorcery spells cost {x} less to cast
where X is the number of creature cards in your graveyard.
You may cast instant or Sorcery Spells from your graveyard,
Once a spell is cast this way you cannot do it
again until your next upkeep.
Spells cast this way are exiled instead of going
to the graveyard