Cheapest priced copy (Archenemy): $3.49 at Card Kingdom, near mint, their price list as of .
Armadillo Cloak 
Enchantment — Aura · Common · Invasion · #229
Enchant creature
Enchanted creature gets +2/+2 and has trample.
Whenever enchanted creature deals damage, you gain that much life.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
6 printings · $3.49 to $39.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Archenemy | 78 | Common | $3.49 | — |
| Duel Decks: Phyrexia vs. the Coalition | 58 | Common | $4.99 | — |
| Eternal Masters | 195 | Uncommon | $4.49 | $6.99 |
| Friday Night Magic 2006 | 2 | Rare | — | $11.99 |
| Invasion | 229 | Common | $3.49 | $39.99 |
| The List | EMA-195 | Uncommon | $4.49 | — |
2 rulings from Wizards of the Coast
- 8 June 2016If Armadillo Cloak enchants a creature you don’t control, you’ll gain life when it deals damage, as long as that damage hasn’t already caused you to lose the game.
- 8 June 2016While Armadillo Cloak’s last ability is similar to lifelink, it isn’t lifelink—it’s a normal triggered ability. If a creature you control with lifelink wears an Armadillo Cloak and deals damage, first you’ll gain that much life for lifelink, and then Armadillo Cloak’s triggered ability is put onto the stack. This also means that multiple instances of Armadillo Cloak’s triggered ability do trigger separately.