Cheapest priced copy (Mystery Booster 2): $1.99 at Card Kingdom, near mint, their price list as of .
Equilibrium 
Enchantment · Rare · The List · #EXO-32
Whenever you cast a creature spell, you may pay {1}. If you do, return target creature to its owner's hand.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
5 printings · $1.99 to $199.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Seventh Edition | 71 | Rare | $2.79 | — |
| Seventh Edition | 71★ | Rare | — | $199.99 |
| Exodus | 32 | Rare | $3.49 | — |
| Mystery Booster 2 | 162 | Rare | $1.99 | $9.99 |
| The List | EXO-32 | Rare | $3.99 | — |
3 rulings from Wizards of the Coast
- 1 April 2008A "creature spell" is any spell with the type Creature, even if it has other types such as Artifact or Enchantment. Older cards of type Summon are also Creature spells.
- 1 August 2008The ability is put on the stack immediately after you cast a creature spell, which means the creature that spell will become won't be a legal target.
- 1 August 2008The ability will still resolve even if the spell that triggered it gets countered.