Fiends to Fireballs

Exile all creature cards from all graveyards.
Fiends to Fireballs deals {x} damage to any player,
where {x} is the sum of all exiled cards' converted
mana costs.
If {x} is equal to or bigger than that player's life
total, this spell can't be countered and
it's damage cannot be prevented.
"The recently deceased are not only great to feed
the earth and it's vermin, but also a fire spell if need
came down to be it."