Merchant of Truth is a rare Creature — Angel Detective card from Murders at Karlov Manor Commander (MKC), collector number 322. Current market price: $1.15, TCGplayer market prices via Scryfall.
Flying Whenever a nontoken creature you control dies, investigate. Clues you control have exalted. (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn for each instance of exalted among permanents you control.)