Circle of Fire Calling

{x}: Discard a card with converted mana cost X:
Circle of Fire Calling deals X-1 damage to a
creature or planeswalker target. If it's a creature,
it loses Indestructible, can't be Regenerated this
turn, and if it would die this turn, exile it instead.
"Warlocks cannot rely on the Crow King, but their
supernatural patrons allow the working some rituals
properly much easier for them."