Slifer, the Sky Dragon

As an additional cost to cast this spell, sacrifice three non-token creatures. This spell can't be countered.

Shroud.

Slifer's power and toughness are equal three times the number of cards in your hand.
Whenever a creature enters the battlefield under an opponents control, it gets five -1/-1 counters.
If Slifer, the Sky Dragon is cast or put onto the battlefield without paying it's mana cost, sacrifice it during the end phase.