Cryptic Coat is a rare Artifact — Equipment card from Murders at Karlov Manor Promos (PMKM), collector number 50p. Current market price: $0.63 (foil $0.40), TCGplayer market prices via Scryfall.
When this Equipment enters, cloak the top card of your library, then attach this Equipment to it. (To cloak a card, put it onto the battlefield face down as a 2/2 creature with ward {2}. Turn it face up any time for its mana cost if it's a creature card.) Equipped creature gets +1/+0 and can't be blocked. {1}{U}: Return this Equipment to its owner's hand.