Cheapest priced copy (Urza's Saga): $0.69 at Card Kingdom, near mint, their price list as of .
Antagonism 
Enchantment · Rare · Urza's Saga · #173
At the beginning of each player's end step, this enchantment deals 2 damage to that player unless one of their opponents was dealt damage this turn.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
1 printing · $0.69 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Urza's Saga | 173 | Rare | $0.69 | — |
One ruling from Wizards of the Coast
- 4 October 2004It looks back over the entire turn even if this card was not on the battlefield at the time.