Cheapest priced copy (Modern Masters): $0.39 at Card Kingdom, near mint, their price list as of .
Worm Harvest 
Sorcery · Rare · Commander 2016 · #238
Create a 1/1 black and green Worm creature token for each land card in your graveyard.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $0.39 to $9.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2016 | 238 | Rare | $0.59 | — |
| Commander 2018 | 194 | Rare | $0.59 | — |
| Eventide | 131 | Rare | $0.49 | $9.99 |
| Modern Masters | 195 | Uncommon | $0.39 | $1.49 |
8 rulings from Wizards of the Coast
- 1 August 2008A retrace card cast from your graveyard follows the normal timing rules for its card type.
- 1 August 2008When a retrace card you cast from your graveyard resolves, fails to resolve, or is countered, it's put back into your graveyard. You may use the retrace ability to cast it again.
- 1 August 2008If you cast Worm Harvest from your graveyard by using retrace, the land you discard as an additional cost will be counted by Worm Harvest when it resolves.
- 1 August 2008If the active player casts a spell that has retrace, that player may cast that card again after it resolves, before another player can remove the card from the graveyard. The active player has priority after the spell resolves, so they can immediately cast a new spell. Since casting a card with retrace from the graveyard moves that card onto the stack, no one else would have the chance to affect it while it's still in the graveyard.
- 1 August 2008Casting a card by using its retrace ability works just like casting any other spell, with two exceptions: You're casting it from your graveyard rather than your hand, and you must discard a land card in addition to any other costs.
- 13 July 2018Casting a card with retrace from your graveyard follows the normal timing rules for its card type.
- 13 July 2018When a retrace card you cast from your graveyard resolves or is countered, it's put back into your graveyard. You may use the retrace ability to cast it again. If it's your turn, you may do so before any other player may take actions to try to remove it from your graveyard.
- 13 July 2018Casting a card by using its retrace ability works just like casting any other spell, with two exceptions: You're casting it from your graveyard rather than your hand, and you must discard a land card in addition to any other costs.