Cheapest priced copy (Duel Decks: Ajani vs. Nicol Bolas): $0.35 at Card Kingdom, near mint, their price list as of .
Hellfire Mongrel 
Creature — Elemental Dog · 2/2 · Uncommon · Zendikar · #130
At the beginning of each opponent's upkeep, if that player has two or fewer cards in hand, this creature deals 2 damage to that player.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Ajani vs. Nicol Bolas | 48 | Uncommon | $0.35 | — |
| Zendikar | 130 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 1 October 2009In a Two-Headed Giant game, this ability will potentially trigger twice at the beginning of the opposing team’s upkeep — once for each player on that team.
- 1 October 2009Hellfire Mongrel’s triggered ability has an “intervening ‘if’ clause.” That means (1) the ability won’t trigger at all unless the opponent whose turn it is has two or fewer cards in hand as their upkeep starts, and (2) the ability will do nothing if that player has three or more cards in hand by the time it resolves.