Basil Karlo was a B-list actor who went insane with anger when Dread Castle, a classic horror movie he starred in, was remade with a different actor in the leading role
Karlo proceeded to kill several members of the cast while dressed up as the Clayface Killer, a character he portrayed in a different film, intending to finish his killing spree by killing the actor who replaced him, before he was stopped and unmasked by Batman and Robin. Although Karlo soon managed to escape incarceration and attempted to murder Bruce Wayne's fiancé Julie Madison, he was again foiled by the Dynamic Duo and was sent back to prison
While Karlo was left in prison, several other individuals would take on the mantle of Clayface for themselves. The second Clayface, Matt Hagen, was a treasure hunter who accidentally fell into a radioactive pool of protoplasm, allowing him to assume a clay-like form able to morph into almost anything he desired
This form was only temporary, however, and he had to continue immersing himself in the protoplasm in order to maintain his powers. During the Crisis on Infinite Earths, Hagen was killed by one of the Anti-Monitor's shadow demons
The third Clayface, Preston Payne, was a scientist who worked at S.T.A.R. Labs looking for a cure for his hyperthyroidism. In order to achieve this, he took a sample of the then-living Matt Hagen's blood and isolated an enzyme that he injected into his bloodstream. While Payne was initially able to maintain his own appearance, his flesh began to melt while on a date with his girlfriend; when he grabbed her arm, she dissolved into protoplasm
Constructing an exoskeleton suit in order to support his flesh and contain his condition, Payne learned that he had to spread his dissolving contagion onto others in order to survive, feeling excruciating pain if he did not dissolve anyone. As his sanity eroded, Payne began to fall in love with a mannequin he named "Helena'" believing that she was the only person he could touch without dissolving her
The fourth Clayface was Sondra Fuller, also known as "Lady Clay". A member of the villainous team Strike Force Kobra, Fuller was willingly transformed by her employers' technologies, giving her powers similar to those of Matt Hagen, although hers were permanent
Around 8 years after his imprisonment, Karlo was visited by Fuller and convinced her to help him form the Mud Pack; an alliance consisting of himself, Sondra and Payne with the common goal of eliminating Batman. However, Basil also secretly plotted to betray his comrades and obtain their powers for himself. He even tried to revive Hagen in hopes of recruiting him to the Mud Pack as well, but to no avail
After the group appeared to have defeated Batman, Karlo stole blood samples from the other Clayfaces and forced a doctor to inject the samples into him, transforming Basil into the Ultimate Clayface. Basil then used his new powers to almost kill Batman and the superheroine Looker in a showdown, until Looker used her psychokinesis to overload Karlo's abilities, causing him to melt through the Earth's crust
Several other individuals took on the mantle following the Mud Pack incident, including Cassius Payne (nicknamed 'Clay'), the son of Preston Payne and Sondra Fuller. Other Clayfaces were company DEO Dr. Peter 'Claything' Malley (transformed following contact with a skin sample of Cassius), former army soldier Todd Russell, Gotham firefighter Johnny Williams (who gained his powers after an explosion at a chemical plant, leading to him being manipulated by Hush and the Riddler in his desperation for a cure), and an unidentified Clayface operating in Japan