Nullios, Troll Outcast

You may cast creature spells from your graveyard
by paying three life as well as any other costs.
At the beginning of combat on your turn, each
player puts the top two cards of their library into
their graveyard, sacrifices a creature, and returns
a creature card from their graveyard onto the
battlefield. If a player can't sacrifice a creature,
instead they discard their hand.