Cheapest priced copy (Modern Horizons 2): $0.35 at Card Kingdom, near mint, their price list as of .
Patchwork Gnomes 
Artifact Creature — Gnome · 2/1 · Common · Ultimate Masters · #231
Discard a card: Regenerate this creature. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
4 printings · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Modern Horizons 2 | 299 | Uncommon | $0.35 | $0.49 |
| Odyssey | 306 | Uncommon | $0.35 | $0.79 |
| Tempest | 299 | Uncommon | $0.39 | — |
| Ultimate Masters | 231 | Common | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 18 June 2021Patchwork Gnomes can regenerate even if it isn't in combat, it's already tapped, or it's undamaged.
- 18 June 2021Activating the ability creates a replacement effect that acts like a shield, replacing the next time Patchwork Gnomes would be destroyed that turn. This shield works against effects that try to destroy Patchwork Gnomes or lethal damage that would be dealt to Patchwork Gnomes.
- 18 June 2021You can activate the regeneration ability even if Patchwork Gnomes isn't at risk of being destroyed. Sometimes you need to discard cards. We understand.