Cheapest priced copy (Avatar: The Last Airbender Eternal): $3.99 at Card Kingdom, near mint, their price list as of .
Fervor 
Enchantment · Rare · Classic Sixth Edition · #174
Creatures you control have haste. (They can attack and {T} as soon as they come under your control.)
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
6 printings · $3.99 to $139.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Classic Sixth Edition | 174 | Rare | $5.99 | — |
| Seventh Edition | 181 | Rare | $5.99 | — |
| Seventh Edition | 181★ | Rare | — | $139.99 |
| Magic 2013 | 129 | Rare | $5.99 | $12.99 |
| Avatar: The Last Airbender Eternal | 29 | Mythic | $3.99 | $4.49 |
| Weatherlight | 99 | Rare | $5.99 | — |
One ruling from Wizards of the Coast
- 1 July 2012If an attacking creature loses haste, perhaps because Fervor leaves the battlefield after attackers have been declared, it won't be removed from combat.