Adrian is a main character of the fourth Felidae book (Das Duell), he's a young and cool tomcat that during the novel is shown as a rival of Francis. He is an American Wirehaired, with a shimmering red tabby coat with brown spots, and black and creamy white badge.
Like Francis, Adrian is extremely smart and gifted with a logical and deductive mind: overcoming in some moments the similar investigative skills of Francis.
Unlike Francis, he seems to be less interested in others and seems to take pleasure in boasting. This behavior and his success cause a depressive feeling in Francis (remarked by Francis's awareness of becoming an older cat)