Merphistophelin

Whenever Merphistophelin attacks, you may sacrifice a creature. If you do, Merphistophelin
gains power and toughness equal to the sacrificed creatures converted mana cost, and gains
flying until the end of turn.
While Merphistophelin is defending, if it were
to take damage, you may pay {4}. If you do, Merphistophelin takes no damage, gains flying,
and power and toughness equal to equal to the defended creatures power until the end of your
next turn.