Zombie Army

When Zombie Army enters the battlefield, put all creature cards from all graveyards onto the battlefield under your control as black zombie creatures.
Whenever a creature is sent to the graveyard, you may pay {3} to put it onto the battlefield under your control instead as a black zombie creature.
You may cast creature cards from any graveyard by paying mana equal to the card's converted mana cost. It is a black zombie creature.