Sadaka, Apex of Pain

{4}{b/g}{r}{r} (If you cast this spell for its mutate cost,
put it over or under target non-Human creature you
own. They mutate into the creature on top plus all abilities from under it.)
Flying, haste
Whenever this creature mutates, you may
sacrifice any number of creatures.
Sadaka, Apex of Pain deals damage equal to the
total power of all creatures sacrificed to target
player.