Koremata's Final Stand

Spellshrivel {2} (As you cast this spell, you may pay its spellshrivel cost. If you do, this spell can't be countered.)
You may cast this spell as if it had flash if you pay an extra {2} while casting it.
Destroy all creatures. They can't be regenerated. Each opponent loses twice X life and discards X cards, where X is the number of creatures destroyed this way.