Slifer the Sky Dragon

Hexproof
You can cast this card by tributing creatures with a
total mana value of this creature's mana cost.
Slifer's power and toughness are each equal to the
number of cards in your hand. When a creature an
opponent controls enters the battlefield, inflict 3
damage to it.
Triad (You can have up to three commanders if
they each have Triad.)