Yog-Sothoth

Protection from everything, Trample, Flying
Yog-Sothoth's power and toughness are both
equal to the amount of cards in your library.
When Yog-Sothoth enters the battlefield, if no
mana was paid to cast it, you lose life equal to the amount of cards in your library.
When Yog-Sothoth leaves the battlefield, return
it to your hand.