Ragnarok

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Destroy all non-God, non-Avatar creatures with converted mana cost X or less. For each creature destroyed this way, its controller takes 1 damage and may create a 2/2 black Zombie creature token or a 1/1 white Spirit creature token with flying. For each token made this way you gain 1 life.