Cheapest priced copy (Ikoria: Lair of Behemoths): $0.35 at Card Kingdom, near mint, their price list as of .
Necropanther 
Creature — Cat Nightmare · 3/3 · Uncommon · Ikoria: Lair of Behemoths · #196
Mutate {2}{W/B}{W/B} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Whenever this creature mutates, return target creature card with mana value 3 or less from your graveyard to the battlefield.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ikoria: Lair of Behemoths | 196 | Uncommon | $0.35 | $0.49 |
| Ikoria: Lair of Behemoths | 302 | Uncommon | $0.35 | $0.79 |
One ruling from Wizards of the Coast
- 17 April 2020If a card in a player’s graveyard has {X} in its mana cost, X is considered to be 0.