Nick Valentine, Private Eye is a rare Legendary Artifact Creature — Synth Detective card from Fallout (PIP), collector number 906. Current market price: — (foil $3.45), TCGplayer market prices via Scryfall.
Nick Valentine can't be blocked except by artifact creatures. Whenever Nick Valentine or another artifact creature you control dies, you may investigate. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")