Cheapest priced copy (Commander Legends): $0.35 at Card Kingdom, near mint, their price list as of .
Null Caller 
Creature — Vampire Shaman · 2/4 · Uncommon · Oath of the Gatewatch · #88
{3}{B}, Exile a creature card from your graveyard: Create a tapped 2/2 black Zombie creature token.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Legends | 140 | Uncommon | $0.35 | $0.49 |
| Oath of the Gatewatch | 88 | Uncommon | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 22 January 2016Once you activate the ability, it's too late for anyone to interrupt you by trying to remove the creature card from your graveyard.