Detective Comics #607 1989

Detective Comics #607 features "The Mud Pack, Part Four: The China Clay Syndrome." Batman is mentally compromised by Lady Clay, necessitating Looker's intervention into his mind. Basil Karlo, having betrayed the other Clayfaces, forcibly combines stolen blood samples to transform himself into the formidable Ultimate Clayface. This issue is significant for collectors as it marks the first appearance of Basil Karlo in his Ultimate Clayface form and concludes the overarching "Mud Pack" storyline.