Cheapest priced copy (The List): $0.49 at Card Kingdom, near mint, out of stock, their price list as of .
Breaker of Armies 
Creature — Eldrazi · 10/8 · Uncommon · Battle for Zendikar · #3
All creatures able to block this creature do so.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.49 to $3.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Battle for Zendikar | 3 | Uncommon | $0.79Out of stock | $3.99Out of stock |
| The List | BFZ-3 | Uncommon | $0.49Out of stock | — |
3 rulings from Wizards of the Coast
- 25 August 2015If more than one Breaker of Armies is attacking, the controller of each creature that could block them chooses which one that creature blocks. In this case, creatures that can block multiple creatures must block as many attacking Breaker of Armies as possible.
- 25 August 2015If, during its controller’s declare blockers step, a creature the defending player controls is tapped or is affected by a spell or ability that says it can’t block, then it doesn’t block. If there’s a cost associated with having it block, its controller isn’t forced to pay that cost. If they don’t, the creature doesn’t have to block.
- 25 August 2015If a creature can’t legally block Breaker of Armies but could block another attacking creature, it may do so. Likewise, if a creature the defending player controls can’t block Breaker of Armies unless its controller pays a cost, its controller may decline to pay that cost and block a different attacking creature.