Zombified Uprising

When Zombified Uprising enters the battlefield,
swap your graveyard with your library.
For as long as Zombified Uprising is on the battlefield, you may play cards from the top of
your library at half their mana costs. At the
beginning of each end step, if there are no cards
in your library, sacrifice Zombified Uprising,
swap your graveyard with your library and take
damage equal to the number of cards in your
library.