Jupiter, King of the Skies

Pactbound (When you cast this spell, you may exile
a Pactholder creature you control. If you do, reduce
this card's mana cost by {x}, where {x} is the exiled
creature's converted mana cost. When this creature
dies, return the exiled creature to play.)
Flying, First Strike
—
"I am the Lightwyrm, Jupiter - lord of thunder and
light, and master of these peaks! Now shall I be the
gleaming bolt that smites your foes!"