Size: 14cm. Recommended age: 15+ years. Kero, whose full name is Kerberos, is the guardian of the Book of Clow, which contains the powerful Clow Cards. Kero appears in his small, cuddly form, which resembles a stuffed winged lion. In this form, he is known as Kero-chan and is usually a small, cheerful, gluttonous creature with a lively and somewhat mischievous personality.