Cheapest priced copy (Return to Ravnica): $0.49 at Card Kingdom, near mint, their price list as of .
Guild Feud 
Enchantment · Rare · Return to Ravnica · #97
At the beginning of your upkeep, target opponent reveals the top three cards of their library, may put a creature card from among them onto the battlefield, then puts the rest into their graveyard. You do the same with the top three cards of your library. If two creatures are put onto the battlefield this way, those creatures fight each other.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Return to Ravnica | 97 | Rare | $0.49 | $0.49 |
4 rulings from Wizards of the Coast
- 1 October 2012Any abilities that trigger when the two creatures enter will be put on the stack after the fight, even if one or both creatures die.
- 1 October 2012If no creatures or only one creature is put onto the battlefield this way, no fight happens.
- 1 October 2012Players can't cast spells or activate abilities between the creatures being put onto the battlefield and them fighting each other. Notably, you can't respond with a spell like Giant Growth.
- 1 October 2012Guild Feud has one target: the opponent. You'll see what creature that player puts onto the battlefield before revealing the top three cards of your library and deciding whether to put a creature onto the battlefield yourself.