No Witnesses is a rare Sorcery card from Murders at Karlov Manor Promos (PMKM), collector number 27s. Current market price: — (foil $0.50), TCGplayer market prices via Scryfall.
Each player who controls the most creatures investigates. Then destroy all creatures. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")