After being exposed to a strain of the Jackal's Carrion Virus, Dr. William Allen was given all of the Jackal's memories and a variety of powers, mutating into the newest Carrion. He became a major threat to New York City civilians until Spider-Man stopped him.
Carrion later allied himself with the Jackal to wreak havoc in Manhattan. He planned to possess a superhuman and permanently bond with him/her, but the Superior Spider-Man prevented him to do so every time he tried after detecting his presence. When the Superior Spider-Man was confronted by the Avengers about his current behavior, Carrion managed to infect Hyperion and almost bonded with him permanently if not by the combined efforts of the heroes. He was thought to have been destroyed by Spider-Man, but he recomposed himself and returned to the Jackal's lair.
Along with the Mutant-Powered Spider-Clones and the clones of Miles Warren and Gwen Stacy, Carrion helped the Jackal capture both Spider-Man and Scarlet Spider to take some fresh tissue samples to use in his future clonages. They were ultimately defeated by the duo, with both the clones and the collected tissues being destroyed in the explosion of the Jackal's hideout. Carrion was later seen collecting a sample of Kaine's DNA with the Jackal, who wanted to use said sample to create a new Spidercide.