Cheapest priced copy (Commander 2019): $0.49 at Card Kingdom, near mint, their price list as of .
Nightmare Unmaking 
Sorcery · Rare · Commander 2019 · #20
Choose one —
• Exile each creature with power greater than the number of cards in your hand.
• Exile each creature with power less than the number of cards in your hand.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
3 printings · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2019 | 20 | Rare | $0.49 | — |
| New Capenna Commander | 253 | Rare | $0.49 | — |
| Wilds of Eldraine Commander | 114 | Rare | $0.49 | — |
2 rulings from Wizards of the Coast
- 23 August 2019The power of creatures and the number of cards in your hand are checked only as Nightmare Unmaking resolves. Players may respond to the spell knowing the chosen mode to try to save or doom a creature.
- 23 August 2019Because Nightmare Unmaking is on the stack while it's resolving, it won't be counted among the cards in your hand.