Following a deeply troubling childhood which culminated in him burning down an orphanage, Cletus became a serial killer and was eventually convicted for eleven consecutive life sentences. Incarcerated at Ryker's Island Prison, Cletus eventually became cellmates with Eddie Brock, who had been separated from the Venom symbiote. When the alien returned to rescue Eddie, it left behind its asexually-produced offspring. The newborn symbiote bonded to Cletus and amalgamated with his blood, transforming him into the monstrous Carnage.