River Song is a rare Legendary Creature — Human Time Lord Rogue card from Doctor Who (WHO), collector number 436. Current market price: $0.69 (foil $0.93), TCGplayer market prices via Scryfall.
Meet in Reverse — You draw cards from the bottom of your library rather than the top. Spoilers — Whenever an opponent scries, surveils, or searches their library, put a +1/+1 counter on River Song. Then River Song deals damage to that player equal to its power.