Cheapest priced copy (Dragon's Maze): $0.35 at Card Kingdom, near mint, their price list as of .
Mutant's Prey 
Instant · Common · Dragon's Maze · #45
Target creature you control with a +1/+1 counter on it fights target creature an opponent controls. (Each deals damage equal to its power to the other.)
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dragon's Maze | 45 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 15 April 2013If one of the targets is illegal when Mutant’s Prey tries to resolve (for example, if the first target creature no longer has a +1/+1 counter on it), neither creature will deal or be dealt damage.
- 15 April 2013Only a creature with a +1/+1 counter on it can be chosen as the first target of Mutant’s Prey.