In an alternate universe Aunt May had died and put Peter Parker into a state of grief. Spider-Man was captured and cloned by Miles Warren. The two escaped but neither knew which was the clone and which was the original. One changed his name to Ben Reilly, died his hair blonde, adopted a different costume that had impact webbing in addition to web shooters, and called himself the Scarlet Spider. The other kept the original identity and names thinking he was the original.
However, this world's Dr. Connors found that Ben may have been the original and that Peter was the clone, causing Peter to deeply resent and even hate Ben. Once, Ben went after Kingpin, and Peter followed and eventually attacked Ben. During the fight, an open interdimensional portal let a Carnage symbiote was released and attached itself to Peter, sensing his rage. Thus Spider-Carnage was born.
With the means to exact his revenge Peter all but destroyed New York City. With assistance from that world's Kingpin, Spider-Carnage planned to use interdimensional portal technology to destroy every single reality, but kept his true intentions hidden from Fisk. He also used that world's Hobgoblin and Green Goblin to carry out his various tasks, such as destroying buildings and gathering equipment.
Spider-Man arrived and Spider-Carnage had briefly mistaken him for Ben. Just as Spider-Carnage defeated Spider-Man, Madame Web took him away to meet Ben. Ben had teamed up with four others to fight the evil Peter. Ben and the others were successful in stopping Peter's plan but he got away to another dimension, the armored Spider-Man's world. Only one could follow him, so Spider-Man was chosen.
After Spider-Carnage finally came to his senses and sacrificed himself, Ben Reilly was returned to this universe, presumably to help fix it.
- Earth-98311 at Marvel Database