Cheapest priced copy (Magic Origins): $0.35 at Card Kingdom, near mint, their price list as of .
Swift Reckoning 
Sorcery · Uncommon · Ultimate Masters · #39
Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, you may cast this spell as though it had flash. (You may cast it any time you could cast an instant.)
Destroy target tapped creature.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic Origins | 35 | Uncommon | $0.35 | $0.49 |
| Ultimate Masters | 39 | Uncommon | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 22 June 2015Check to see if there are two or more instant and/or sorcery cards in your graveyard as the spell resolves to determine whether the spell mastery ability applies. The spell itself won't count because it's still on the stack as you make this check.
- 7 December 2018The number of instant and/or sorcery cards in your graveyard matters only as you begin to cast Swift Reckoning. Once it's cast, that number doesn't matter and will have no effect on Swift Reckoning resolving.
- 7 December 2018If an effect allows you to cast Swift Reckoning from your graveyard, you need two other instant and/or sorcery cards in your graveyard to cast it as though it had flash.