Cheapest priced copy (Dragons of Tarkir): $0.35 at Card Kingdom, near mint, their price list as of .
Vulturous Aven 
Creature — Bird Shaman · 2/3 · Common · Dragons of Tarkir · #126
Flying
Exploit (When this creature enters, you may sacrifice a creature.)
When this creature exploits a creature, you draw two cards and you lose 2 life.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dragons of Tarkir | 126 | Common | $0.35 | $0.49 |
5 rulings from Wizards of the Coast
- 25 February 2015If the creature with exploit isn’t on the battlefield as the exploit ability resolves, you won’t get any bonus from the creature with exploit, even if you sacrifice a creature. Because the creature with exploit isn’t on the battlefield, its other triggered ability won’t trigger.
- 25 February 2015You can’t sacrifice more than one creature to any one exploit ability.
- 25 February 2015A creature with exploit “exploits a creature” when the controller of the exploit ability sacrifices a creature as that ability resolves.
- 25 February 2015You choose whether to sacrifice a creature and which creature to sacrifice as the exploit ability resolves.
- 25 February 2015You can sacrifice the creature with exploit if it’s still on the battlefield. This will cause its other ability to trigger.