Dilemma in the Morgue

Destroy target creature an opponent controls with converted mana cost X or less. Each opponent loses X life and you gain X life.
"Who would have the audacity to betray us? To murder our only ambassador to the Merfolk in cold blood?! This is heresy of the highest order! Find the one responsible at once. Come empty handed, and you'll remain empty handed the rest of your lives." --- Vona, Butcher of Magan