Obliterate

Spell stack {1}{u}{r} (You may cast this spell as
a sorcery for {1}{u}{r}. If you do, place it face
down on the battlefield as a 2/2 creature with;
When you cast another non-creature spell, you
may flip this spell over and cast it for its spell
stack cost.)
Destroy target creature. Destroy another target creature for each stacked spell you
cast at the same time as this spell.