Sarah Jane Smith is a rare Legendary Creature — Human Detective card from Doctor Who (WHO), collector number 536. Current market price: $0.51 (foil $0.53), TCGplayer market prices via Scryfall.
Whenever you cast a historic spell, investigate. This ability triggers only once each turn. (Artifacts, legendaries, and Sagas are historic. To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") Doctor's companion (You can have two commanders if the other is the Doctor.)