Sif, Spark in the Void

{u}{u}{b}{b}: Discard 2 cards then draw 4 cards.
{x}{x}: Draw X cards, put the top X cards from
the top of your library into your graveyard.
{t}: Sacrifice X permanents then gain
twice that much colorless mana.
When you have fewer than five cards left in your library you win the game.