Slifer, The Sky Dragon

When this card enters the battlefield, sacrifice it
unless you sacrifice two other creatures. If this
card enters the battlefield and it was not cast
from your hand, sacrifice it at the beginning of
the next end step.
Flying, Haste, Hexproof
Creatures come into play under your opponents control with three -1/-1 counters.
Slifer, The Sky Dragon's power and toughness
are equal to the number of cards in your hand.