Cheapest priced copy (Urza's Destiny): $0.35 at Card Kingdom, near mint, their price list as of .
Lurking Jackals 
Enchantment · Uncommon · Urza's Destiny · #62
When an opponent has 10 or less life, if this permanent is an enchantment, it becomes a 3/2 Jackal creature.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
1 printing · $0.35 to $3.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Urza's Destiny | 62 | Uncommon | $0.35 | $3.49 |
3 rulings from Wizards of the Coast
- 4 October 2004Once it becomes a creature, it will not change back into an enchantment if your opponent's life total goes back above 10.
- 4 October 2004Once it becomes a creature, it is no longer an enchantment.
- 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.