Cheapest priced copy (Fifth Edition): $0.35 at Card Kingdom, near mint, their price list as of .
Carapace 
Enchantment — Aura · Common · Homelands · #84a
Enchant creature
Enchanted creature gets +0/+2.
Sacrifice this Aura: Regenerate enchanted creature.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
3 printings · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Fifth Edition | 281 | Common | $0.35 | — |
| Homelands | 84a | Common | $0.35 | — |
| Homelands | 84b | Common | $0.35 | — |
One ruling from Wizards of the Coast
- 4 October 2004This leaves the battlefield when you activate its activated ability, but the enchanted creature won't be regenerated until the ability resolves. In the intervening time, the creature will no longer have the bonus that this had been giving it. This may cause the creature to be destroyed before the regeneration shield is created.