Energizing Electrification

(You may cast a legendary instant only if you control
a legendary creature or planeswalker.)
As an additional cost to cast this spell, have it
deal X damage to each creature you control.
Each creature you control gets +X/+0 and gains
haste and menace until end of turn. If an
creature an opponent controls would die this
turn, exile it instead of putting it into its owners
graveyard.