Cheapest priced copy (Dominaria United): $0.49 at Card Kingdom, near mint, their price list as of .
Temporal Firestorm 
Sorcery · Rare · Dominaria United · #147
Kicker {1}{W} and/or {1}{U} (You may pay an additional {1}{W} and/or {1}{U} as you cast this spell.)
Choose up to X creatures and/or planeswalkers you control, where X is the number of times this spell was kicked. Those permanents phase out.
Temporal Firestorm deals 5 damage to each creature and each planeswalker.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dominaria United | 147 | Rare | $0.49 | $0.49 |
| Dominaria United | 411 | Rare | $0.49 | $0.49 |
| Dominaria United Promos | 147p | Rare | $0.49 | $0.49 |
| Dominaria United Promos | 147s | Rare | — | $0.49 |
7 rulings from Wizards of the Coast
- 9 September 2022You may kick Temporal Firestorm only once for its {1}{W} cost and only once for its {1}{U} cost. You can kick it twice by paying {2}{W}{U}, but you can't kick it twice by paying {2}{W}{W} or {2}{U}{U}. You can't kick it more than twice. Notably, this means that X will always be either one or two if Temporal Firestorm was kicked.
- 8 November 2024If you copy a kicked spell on the stack, the copy is also kicked. If the copied spell is a permanent spell, the token the copy of that spell becomes when it enters is also kicked.
- 8 November 2024If a card or token enters as a copy of a permanent, the new permanent isn't kicked, even if the original was.
- 8 November 2024If a spell's kicker cost was paid, the spell is "kicked."
- 8 November 2024The kicker ability doesn't let you pay a kicker cost more than once.
- 8 November 2024To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions. The spell's mana value remains unchanged, no matter what the total cost to cast it was.
- 8 November 2024If you put a permanent with a kicker ability onto the battlefield without casting it, you can't kick it.