Cheapest priced copy (Duel Decks: Mind vs. Might): $0.35 at Card Kingdom, near mint, their price list as of .
Empty the Warrens 
Sorcery · Rare · Secrets of Strixhaven Mystical Archive · #108
Create two 1/1 red Goblin creature tokens.
Storm (When you cast this spell, copy it for each spell cast before it this turn.)
Legal inCommanderModernLegacyVintage
Banned inPauper
Not legal inBrawlStandardPioneer
12 printings · $0.35 to $12.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Mind vs. Might | 15 | Common | $0.35 | — |
| Dominaria Remastered | 118 | Common | $0.35 | $0.49 |
| Dominaria Remastered | 318 | Common | $0.35 | $0.49 |
| Modern Masters | 112 | Common | $0.49 | $0.49 |
| The List | DDS-15 | Common | $0.35 | — |
| The List | DMR-118 | Common | — | — |
| Secret Lair Drop | 2412 | Rare | — | $7.99 |
| Secrets of Strixhaven Mystical Archive | 43 | Rare | $0.79 | $0.79 |
| Secrets of Strixhaven Mystical Archive | 108 | Rare | $1.99 | — |
| Secrets of Strixhaven Mystical Archive | 173 | Rare | — | $12.99 |
| Time Spiral | 152 | Common | $0.49 | $4.99 |
| Time Spiral Remastered | 162 | Common | $0.35 | $0.49 |
4 rulings from Wizards of the Coast
- 8 December 2022Spells cast from zones other than a player's hand and spells that were countered are counted by the storm ability.
- 8 December 2022The 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.
- 8 December 2022A 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.
- 8 December 2022The 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.