The Countdown Is at One is a rare Sorcery card from The List (Unfinity Foil Edition) (ULST), collector number 28. Current market price: — (foil $0.29), TCGplayer market prices via Scryfall.
Players play a Magic subgame, starting at 1 life and using their libraries as their decks. For the rest of the main game, if a source would deal damage to a player who didn't win the subgame, it deals double that damage to that player instead.