Skeleton Key (SOI) from Shadows over Innistrad, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: Daniel Ljunggren
• Card Text:
  Equipped creature has skulk. (It can't be blocked by creatures with greater power.)
  Whenever equipped creature deals combat damage to a player, you may draw a card. If you do, discard a card.
  Equip 2