Cheapest priced copy (Oath of the Gatewatch): $0.35 at Card Kingdom, near mint, their price list as of .
Immobilizer Eldrazi 
Creature — Eldrazi Drone · 2/1 · Uncommon · Oath of the Gatewatch · #97
Devoid (This card has no color.)
{2}{C}: Each creature with toughness greater than its power can't block this turn. ({C} represents colorless mana.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Oath of the Gatewatch | 97 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 22 January 2016If a creature has already been legally declared as a blocker, Immobilizer Eldrazi’s ability won’t change or undo that block.
- 22 January 2016You compare the power and toughness as you declare blockers, not as Immobilizer Eldrazi’s ability resolves. For example, if you control a 3/3 creature as the ability resolves, then later that turn it gets +0/+1 such that it’s 3/4 as blockers are declared, it won’t be able to block.