Cheapest priced copy (Born of the Gods): $0.35 at Card Kingdom, near mint, their price list as of .
Culling Mark 
Sorcery · Common · Born of the Gods · #120
Target creature blocks this turn if able.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Born of the Gods | 120 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 1 February 2014The controller of the creature chooses which attacking creature that creature blocks.
- 1 February 2014The creature blocks only if it’s able to do so as the declare blockers step begins. If, at that time, the creature is tapped, it’s affected by a spell or ability that says it can’t block, or no creatures are attacking its controller or a planeswalker controlled by that player, then it doesn’t block. If there’s a cost associated with having the creature block, the player isn’t forced to pay that cost. If that cost isn’t paid, the creature won’t block.