Midgardsormr, the Tempest

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, Trample
—
"I am Midgardsormr - lord of malestroms,
master of this land, and the storm that shall keep
you from harm! "