Cheapest priced copy (Rise of the Eldrazi): $0.69 at Card Kingdom, near mint, their price list as of .
Gravity Well 
Enchantment · Uncommon · Rise of the Eldrazi · #185
Whenever a creature with flying attacks, it loses flying until end of turn.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $0.69 to $3.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Rise of the Eldrazi | 185 | Uncommon | $0.69 | $3.49 |
2 rulings from Wizards of the Coast
- 15 June 2010This ability triggers and resolves during the declare attackers step. The creature will no longer have flying by the time blockers are declared.
- 15 June 2010After attackers are declared and any Gravity Well abilities have resolved, a spell or ability that grants flying to a creature will work normally. This includes other abilities that trigger “whenever [a creature] attacks” (such as the one Order of the Golden Cricket has).