W.D. Gaster

As an additional cost to cast W.D. Gaster, exile the top three cards of your library.
When you cast W.D. Gaster, you may cast an instant or sorcery card you own from exile. If that spell destroys a creature as it resolves, exile this spell, then you may cast a card you own named W.D. Gaster from exile without paying its mana cost.