Cheapest priced copy (March of the Machine): $0.99 at Card Kingdom, near mint, their price list as of .
Borborygmos and Fblthp 
Legendary Creature — Cyclops Homunculus · 6/5 · Mythic · March of the Machine · #219
Whenever Borborygmos and Fblthp enters or attacks, draw a card, then you may discard any number of land cards. When you discard one or more cards this way, Borborygmos and Fblthp deals twice that much damage to target creature.
{1}{U}: Put Borborygmos and Fblthp into its owner's library third from the top.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $0.99 to $3.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| March of the Machine | 219 | Mythic | $1.29 | $0.99 |
| March of the Machine | 303 | Mythic | $0.99 | $1.49 |
| March of the Machine Promos | 219p | Mythic | $0.99 | $1.49 |
| March of the Machine Promos | 219s | Mythic | — | $3.49 |
4 rulings from Wizards of the Coast
- 14 April 2023You can’t discard nonland cards, even if you want to.
- 14 April 2023The first ability of Borborygmos and Fblthp triggers and goes on the stack without a target. If you discard one or more land cards, the second “reflexive” triggered ability will trigger. You’ll choose the target creature for that second ability at that time.
- 14 April 2023If there are one or fewer cards in your library, Borborygmos and Fblthp is put on the bottom of your library.
- 14 April 2023Only the controller of Borborygmos and Fblthp can activate its last ability, and only if it’s on the battlefield.