Cheapest priced copy (Shadowmoor): $0.35 at Card Kingdom, near mint, their price list as of .
Gravelgill Duo 
Creature — Merfolk Rogue Warrior · 2/1 · Common · Shadowmoor · #165
Whenever you cast a blue spell, this creature gets +1/+1 until end of turn.
Whenever you cast a black spell, this creature gains fear until end of turn. (It can't be blocked except by artifact creatures and/or black creatures.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Shadowmoor | 165 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 1 May 2008An object that's both of the listed colors will cause both abilities to trigger. You can put them on the stack in either order.