Cheapest priced copy (The List): $17.99 at Card Kingdom, near mint, their price list as of .
Lurking Predators 
Enchantment · Rare · Magic 2010 · #190
Whenever an opponent casts a spell, reveal the top card of your library. If it's a creature card, put it onto the battlefield. Otherwise, you may put that card on the bottom of your library.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $17.99 to $94.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2016 | 156 | Rare | $18.99 | — |
| Jumpstart | 410 | Rare | $18.99 | — |
| Magic 2010 | 190 | Rare | $19.99 | $94.99Out of stock |
| The List | M10-190 | Rare | $17.99 | — |
3 rulings from Wizards of the Coast
- 1 October 2009A "creature card" is any card with the type creature, even if it has other types such as artifact, enchantment, or land. Older cards of type summon are also creature cards.
- 1 October 2009If an opponent casts a spell, this ability triggers and is put on the stack on top of that spell. This ability will resolve (meaning that a revealed creature card will enter) before the spell resolves.
- 1 October 2009You must put the revealed card onto the battlefield if it's a creature card. If it's not a creature card and you don't put it on the bottom of your library, it stops being revealed and simply remains on top of your library.