The Clow is the book within which the Clow Cards are placed. Clow Cards are magical cards created by a sorceror, Clow Reed, who had super "powers." For example, the card of fire would have the magic of fire, the card of wind would have the magic of wind, and so on. Each card has its own life and does whatever it wants. Because they have strong "powers", normal things cannot win against them. Therefore, Clow Reed put the cards into a book called The Clow, and placed the Beast of the Seal, Cerberus (or Kerberos), on the cover to prevent the cards from turning bad. The book is locked by the Key of the Seal. As you unlock it and open the book, you can find a hole where the Clow Cards are put. In any case, Cerberus (Kerberos) fell asleep. Sakura found the book in the basement of her house, and accidentally scattered the cards away. She must capture the Clow Cards back to prevent the happening of a disaster!