Truth or Dare is a rare Sorcery card from Mystery Booster Playtest Cards 2021 (CMB2), collector number 32. Current market price: $0.34, TCGplayer market prices via Scryfall.
Target opponent chooses one — • Truth — That player plays with their hand revealed for the rest of the game. • Dare — Mill all but the bottom ten cards of that player's library. (To mill, put the top card of that library into its owner's graveyard.)