Lolth, the Schemer

Lolth costs {x} less to cast, where X is the
number of cards in your graveyard.
Exile X cards from your graveyard: You may cast target card with converted mana cost X from
your graveyard this turn. If you exile a land this
way, create a 1/1 spider creature token.
Whenever you would draw a card, you may
instead put a card you own from exile into your
hand. If you do, sacrifice a creature.