Diamondhead first appeared in Nova vol 1 #3 (Nov 1976), and was created by Marv Wolfman and Sal Buscema.
Arch Dyke was mutated by a diamond-powered laser while attempting to steal some precious gems. He forms the criminal gang Terrible Trio with the Sphinx and Doctor Sun. Along with his allies, Nova, and the Champions of Xandar, Diamondhead goes to Xandar on Nova's spacecraft.
Once there, Diamondhead causes the death of one of the Champions, and Diamondhead is left to float in space.
Later, Diamondhead was seen as a prisoner on the Stranger's laboratory world. He somehow escapes and returns to Earth. Diamondhead uses this information to locate Nova's parents' house and patiently waits until his nemesis comes home. When Nova returns to Earth after the Annihilation War, Diamondhead attacks him. Nova easily defeats Diamondhead and takes him back to prison.
After the sacrifice of Richard Rider at the end of Thanos Imperative, Diamondhead ambushes the new scrappy Nova (Sam Alexander), but is easily defeated and left stranded in the desert.
Diamondhead's body is basically one large diamond, making him incredibly strong and incredibly resistant to injury and harm. According to Nova, he can regrow destroyed limbs, given time.