
Instant
Target player mills three cards.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Iconic red Storm payoff that wins via direct damage instead of mill.

Classic Storm finisher draining life for each copy.

Efficient two-card mill spell in same self-mill/mill strategy.

Scalable mill with kicker to deck out opponents.

Mills half a library for big single-shot self-mill or attack.

Heavy targeted mill spell for graveyard/decking plans.

Doubles spells like Storm enabler to fuel huge copy counts.

Storm-friendly payoff that gains life and can win after a chain.
Spells cast from zones other than a player's hand and spells that were countered are counted by the storm ability.
The copies are put directly onto the stack. They aren't cast and won't be counted by other spells with storm cast later in the turn.
A copy of a spell can be countered like any other spell, but it must be countered individually. Countering a spell with storm won't affect the copies.
You may choose new targets for any of the copies. You can make different choices for each copy.
The triggered ability that creates the copies can itself be countered by anything that can counter a triggered ability. If it is countered, no copies will be put onto the stack.