Slifer the Sky Dragon

Flying, Shroud, Vigilance
Slifer the Sky Dragon can't be countered.
As an additional cost to cast this spell, you must
sacrifice 3 creatures.
Slifer the Sky Dragon's power and toughness are
each equal to the number of cards in your hand.
Whenever a creature enters the battlefield under
your opponents control, put two -1/-1 counters
on it.