Each player puts the top two cards of their library into their graveyard. Then you put a creature card from a graveyard onto the battlefield under your control.
6/8/2016 Extract from Darkness doesn’t target a creature card. You choose which card you’re putting onto the battlefield as it resolves. You can choose any creature card in a graveyard at that time, including one just put into a graveyard by Extract from Darkness. If there are no creature cards in graveyards at that time, Extract from Darkness simply finishes resolving.