Cheapest priced copy (Theros): $0.49 at Card Kingdom, near mint, their price list as of .
Polis Crusher 
Creature — Cyclops · 4/4 · Rare · Theros · #198
Trample, protection from enchantments
{4}{R}{G}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
Whenever this creature deals combat damage to a player, if this creature is monstrous, destroy target enchantment that player controls.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Theros | 198 | Rare | $0.49 | $0.49 |
5 rulings from Wizards of the Coast
- 15 September 2013Monstrous isn't an ability that a creature has. It's just something true about that creature. If the creature stops being a creature or loses its abilities, it will continue to be monstrous.
- 15 September 2013An ability that triggers when a creature becomes monstrous won't trigger if that creature isn't on the battlefield when its monstrosity ability resolves.
- 15 September 2013“Protection from enchantments” means that Polis Crusher can't be enchanted, it can't be targeted by Aura spells or by abilities of enchantments, all damage that would be dealt to it by enchantments is prevented, and it can't be blocked by enchantment creatures. Notably, it doesn't have protection from enchanted creatures (unless those creatures are also enchantments).
- 15 September 2013Once a creature becomes monstrous, it can't become monstrous again. If the creature is already monstrous when the monstrosity ability resolves, nothing happens.
- 15 September 2013Polis Crusher must be monstrous as it deals combat damage to a player in order for its last ability to trigger. Once the ability triggers, it resolves even if Polis Crusher isn't on the battlefield at that time.