Cheapest priced copy (Adventures in the Forgotten Realms): $0.35 at Card Kingdom, near mint, their price list as of .
Targ Nar, Demon-Fang Gnoll 
Legendary Creature — Gnoll · 2/2 · Uncommon · Adventures in the Forgotten Realms · #234
Pack tactics — Whenever Targ Nar attacks, if you attacked with creatures with total power 6 or greater this combat, attacking creatures get +1/+0 until end of turn.
{2}{R}{G}: Double Targ Nar's power and toughness until end of turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Adventures in the Forgotten Realms | 234 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 23 July 2021If a creature's power is less than 0 when it's doubled, instead that creature gets -X/-0, where X is how much less than 0 its power is. For example, if an effect has given a 2/2 creature -4/-0 so that it's a -2/2 creature, doubling its power and toughness gives it -2/+2, and it becomes a -4/4 creature.
- 23 July 2021If an effect instructs you to "double" a creature's power, that creature gets +X/+0, where X is its power as that effect begins to apply. The same is true for toughness.