Cheapest priced copy (The List): $0.35 at Card Kingdom, near mint, their price list as of .
Serpentine Curve 
Sorcery · Common · The List · #STX-52
Create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it, where X is one plus the total number of instant and sorcery cards you own in exile and in your graveyard.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The List | STX-52 | Common | $0.35 | — |
| Strixhaven: School of Mages | 52 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 16 April 2021Serpentine Curve itself is not yet in your graveyard when you determine the value of X.
- 16 April 2021If you own face-down cards in exile, they won’t count toward the value of X, even if you’re allowed to look at them and you know they are instant or sorcery cards.