Cheapest priced copy (Innistrad: Double Feature): $0.35 at Card Kingdom, near mint, their price list as of .
Biolume Egg // Biolume Serpent 
Creature — Serpent Egg // Creature — Serpent · 0/4 · Uncommon · Innistrad: Crimson Vow · #49
Defender
When this creature enters, scry 2.
When you sacrifice this creature, return it to the battlefield transformed under its owner's control at the beginning of the next end step.
Sacrifice two Islands: This creature can't be blocked this turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Innistrad: Double Feature | 316 | Uncommon | $0.35 | $0.49 |
| Innistrad Remastered | 54 | Uncommon | $0.35 | $0.49 |
| Innistrad Remastered | 455 | Uncommon | $0.35 | $0.49 |
| Innistrad: Crimson Vow | 49 | Uncommon | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 19 November 2021If a permanent that isn't a double-faced card becomes a copy of Biolume Egg and then is sacrificed, that card can't be returned to the battlefield transformed. It will remain in the graveyard.
- 19 November 2021You can't sacrifice Biolume Egg unless another effect allows you to.
- 19 November 2021You may sacrifice any two lands with the subtype Island to activate Biolume Serpent's ability, even if they aren't basic or aren't named Island.