Cheapest priced copy (Champions of Kamigawa): $0.35 at Card Kingdom, near mint, their price list as of .
Jade Idol 
Artifact · Uncommon · Champions of Kamigawa · #256
Whenever you cast a Spirit or Arcane spell, this artifact becomes a 4/4 Spirit artifact creature until end of turn.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Champions of Kamigawa | 256 | Uncommon | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 1 August 2008A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn’t matter how long the permanent has been a creature.