Cheapest priced copy (The Lost Caverns of Ixalan): $0.35 at Card Kingdom, near mint, their price list as of .
Soulcoil Viper 
Creature — Snake · 2/3 · Uncommon · The Lost Caverns of Ixalan · #120
{B}, {T}, Sacrifice this creature: Return target creature card from your graveyard to the battlefield with a finality counter on it. Activate only as a sorcery. (If a creature with a finality counter on it would die, exile it instead.)
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Lost Caverns of Ixalan | 120 | Uncommon | $0.35 | $0.49 |
5 rulings from Wizards of the Coast
- 10 November 2023Because you choose the target of Soulcoil Viper's ability before you pay the cost of sacrificing it, Soulcoil Viper can't be the target of its own ability.
- 10 November 2023Finality counters work on any permanent, not only creatures. If a permanent with a finality counter on it would be put into a graveyard from the battlefield, exile it instead.
- 10 November 2023Multiple finality counters on a single permanent are redundant.
- 10 November 2023Finality counters don't stop permanents from going to zones other than the graveyard from the battlefield. For example, if a permanent with a finality counter on it would be put into its owner's hand from the battlefield, it does so normally.
- 10 November 2023Finality counters aren't keyword counters, and a finality counter doesn't give any abilities to the permanent it's on. If that permanent loses its abilities and then would go to a graveyard, it will still be exiled instead.