Basil Karlo was an actor who was driven mad when he learned of a remake of his classic horror film The Terror, even though he was to be one of the advising staff. Donning the mask of the film's villain, Clayface, he embarked on a murder spree among the cast and crew of the remake. He was foiled by Batman and Robin. He reappeared after the prison ambulance he was riding in plunged off a cliff. He once again donnned the mask of Clayface and targeted Bruce Wayne's fiancee, Julie Madison. Once again, the Dynamic Duo foiled the evil Karlo.
Much later, Karlo languished in a prison hospital, when Sondra Fuller visited him out of curiosity. Karlo proposed an alliance between all living Clayfaces to kill Batman. Even though the Mud Pack, as the group called itself, was defeated, Karlo managed, by tricking his allies, to imbue himself with abilities similar to those of Preston Payne and Sondra Fuller. He was defeated by the combined efforts of Batman and Looker of the Outsiders, by overloading his abilities, making him melt into the ground. Sinking into the earth's crust when he lost control of his power, he managed to survive, and now his body sports crystals similar to quartz that endow him with greater powers. Karlo was able to escape his underground prison when Gotham City was struck by the great Cataclysm. He was able to capture Batman and was about to kill him, but he got into a feud with Mr. Freeze about who should kill the Caped Crusader. With that distraction, Batman soundly defeated both of them.
During the "No Man's Land" storyline, Basil Karlo held Poison Ivy, who was in charge of producing fresh vegetables for the remaining people in the city, prisoner in Robinson Park. Poison Ivy eventually battled and defeated Karlo, sinking him deep into the ground. It appears that the Ultimate Clayface is destroyed in this battle, but he resurfaced as a member of the Secret Society of Super Villains. Later, he sought to increase his already formidable powers by absorbing Wonder Woman (a clay construct similar to him), giving him an amount of power that bordered on invulnerability. While he was successful in absorbing the heroine, he was ultimately forced to release her.
Basil Karlo was among the members of the Injustice League and was among the villains seen in Salvation Run. He can be seen as the member of Libra's Secret Society of Super Villains. In the second issue of Final Crisis, he triggered an explosion at the Daily Planet.
Black Mask attempted to control Clayface by implanting a device in his body. He escaped Black Mask but was captured and imprisoned by the Outsiders.
Battle vs. Sandman (by CuchulainSetanta)
Deep in Gotham City, the super-criminal Sandman bursts into the Monarch movie theatre, planning on robbing the joint. He frightens off the patrons, and soon breaks open the safe where the theatre's money is stored. Before he can leave, however, he hears something in the ceiling. Before Sandman knows what is happening, Clayface breaks through, having planned to destroy the theatre that shows his old films.
The two supervillains size each other up, before Clayface takes a swing at Sandman. Sandman avoids the attack by dispersing into a sandstorm, then rushes Clayface, reforming and knocking the former actor through a wall into the back alley. Sandman goes in for another hit, but Clayface counters with a strike of his own. The men duel, shifting their bodies into a variety of weapons, each countering the other's attacks.
Finally, Sandman seems to gain an advantage, using a sand-mace to smash in Clayface's head. Clayface staggers, and Sandman grins, thinking he has one. Suddenly, however, he hears Clayface laughing as his head reforms over Sandman's hand. Without warning, Clayface thrusts one of his arms into Sandman's form. As Clayface withdraws, Sandman begins to scream in agony before falling apart into protoplasm. Clayface turns and sees the Batsignal in the sky. He thrusts his fist in the air, shouting "You're next, Batman!"
While both were very similar, Clayface is gigantic, can melt others down to protoplasm and every one of his cells work together better than Sandman's. When Sandman attacks Clayface, he will get stuck in him and Clayface will start melting him.
Battle vs. Eddie Brock (by Detective Loki)