Slifer the sky Dragon

As an additional cost sacrifice 3 creatures if you dont send this card to the GY.
This spell cannot be negated. When this creature enters the battlefield, cards and effects cannot be activated.
Once per turn, during the End Phase, if this card was Summoned without paying the mana cost : Send it to the GY. Power and toughness is X where X is the number of cards in your hand.
If a creature enters the battlefield under your opponent's control it gains -5/-5