Diabolic Rejoinder

Counter target spell unless its caster pays life equal to its converted mana cost.
If they do, you gain that much life. If they do not, create an X/X black Demon creature token with flying, where X is the countered spell's converted mana cost.
Subsection B of Article 13, the signatory hereafter known as "The Victim," agrees to pay the guarantor hereafter known as "Mephisto"....