The Clow Book is a book containing a collection of mysterious and powerful magic cards titled "Clow Cards". originally owned by Clow Reed. It is first seen on Episode 1 when Sakura Kinomoto goes inside of their house's basement after hearing a loud noise coming from the basement. The book's cover is designed as a yellow lion named Cerberus which is the guardian of the Clow Cards. When Sakura opened it, she first saw The Windy card, and she reads its name loud, causing the cards to escape the Clow Book where they are scattered all over the city.