Constellation Serpent

Whenever Constellation Serpent enters the battlefield or attacks, you may exile up to two
target cards from a graveyard. For each creature
card exiled this way, create a 1/1 blue and black Abyssal creature token. For each noncreature
card exiled this way, its owner mills 2 cards.
When Constellation Serpent dies, you may return target Abyssal card with mana value less than the number of cards in an opponent's graveyard
from your graveyard to your hand.