Simic Seiron, Biomancer

Rush {x}{g}{u} (You may cast this card from your graveyard for its rush cost. If you do, it's exiled when it enters the battlefield.)
When Simic Seiress, Biomancer enters the battlefield, distribute X +1/+1 counters among any number of creatures on the battlefield.
Whenever a creature with a +1/+1 counter on it attacks, you may draw a card.