Cryptex is a rare Artifact card from Murders at Karlov Manor (MKM), collector number 251. Current market price: $0.15 (foil $0.10), TCGplayer market prices via Scryfall.
{T}, Collect evidence 3: Add one mana of any color. Put an unlock counter on this artifact. (To collect evidence 3, exile cards with total mana value 3 or greater from your graveyard.) Sacrifice this artifact: Surveil 3, then draw three cards. Activate only if this artifact has five or more unlock counters on it.