The symbiote that would later be known as Venom is an alien parasite created by the dark elder god Knull and cast into exile by the rest of its kind. After Knull's imprisonment, the symbiote was taken by Kree scientists and bonded to Tel-Kar, but had its memories sealed upon being separated from him. Eventually the symbiote joined a group of malicious symbiotes, but was imprisoned out of fear its relative benevolence would contaminate the Hive.
The symbiote's prison was transported to Battleworld by the Beyonder, where it was unwittingly freed by Spider-Man, who it bonded to - taking on the appearance of a black costume. After discovering that the suit was actually a living being that sought to permanently merge with him, Spider-Man rejected the symbiote and eventually tried to kill it.
The symbiote bonded with the former reporter, Eddie Brock, who blamed Spider-Man for having ruined his career after discrediting his story about the Sin-Eater. The mutual hatred they both had for Spider-Man caused the symbiote to bond with Eddie, taking the name Venom. Despite being mostly bonded to Eddie Brock, the symbiote has bonded to several hosts, the most prominent of whom are: Mac Gargan, Flash Thompson, and Lee Price.