Diamond Hammer was created by Danny Fingeroth and Ron Lim in 1995 and first appeared in The Amazing Spider-Man: Friends and Enemies # 1.
Carl was working with a crook named Elias Flynn while walking by Madison Square Park when they notice people standing near a glow in the bushes. There, Carl and Elias take two of the seven crystals that were glowing. The crystals shower everyone in light and baffled by the display, they exchange information before disbanding. Later Carl, while attempting to steal a car, covered his body in a crystal like coating and ripped the car door off. Eventually Carl meets up with the others accompanied by Flynn, all of whom had acquired powers as Carl did. Its at that time Flynn reveals he gained the ability to control the others, though Carl mostly acts on Flynn's demands largely by choice still. Carl is trained with the others and dubbed the Metahumes by Flynn, gainin the name Diamond Hammer. After Flynn sends the Metahumes to rob a bank he decides to its time to sell their talents off, but the deal goes sour and they face off against the hired armored muscle the Seekers. The Seekers are defeated easily enough but then Spider-Man, Speedball, Nova, and Darkhawk intervened. Before the heroes could stop them Flynn hostages and they got away. Carl and the others entered the hideout but Flynn was cornered and killed by a group called the Hostiles. With Flynn dead, the team was able to shake off his mind control, but knowing Carl's loyalty some of them attack him. Before the conflict grew the Hostiles capture the team and later reveal to have taken their loved ones hostage to ensure cooperation. While the Metahumes were being tested on by the Hostiles, Spider-Man and the others eventually find them and break them out. Once free Carl takes on a more bulky crystal form in rage. In the fight the Hostiles use the crystals and become a crystals monster. It takes everyone to fight it down, but they manage to subdue it and revert the Hostiles back to human form. With the threat seemingly ended the Metahumes are left to ponder their futures. Knowing the ill-will the others hold towards him, Carl leaves to chart his path alone.
Diamond Hammer has the power to either cover his body in or transform it into crystal. In this form he gains super strength and durability.
He later shows a sort of berserker like transformation where in he increases in size and forms spikes. This form seems to increase his strength as well.