Carapace

Enchant creature
Enchanted creature gets +0/+2.
Sacrifice this Aura: Regenerate enchanted creature.

Masters Edition II

Enchant creature
Enchanted creature gets +0/+2.
Sacrifice Carapace: Regenerate enchanted creature.

"Now *that's* a fashion statement."
—Devin, faerie noble

Fifth Edition

Enchanted creature gets +0/+2.
Sacrifice Carapace: Regenerate enchanted creature.

"The tougher to crack, the sweeter the snack."
—Kakra, Sea Troll

Homelands

Target creature gets +0/+2.
o0: Sacrifice Carapace to regenerate creature Carapace enchants.

"Now, *that's* a fashion statement."
—Devin, Faerie Noble

This 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.