Symbiotes are a fictional race of extraterrestrial amorphous parasites and one of them gave rise to Venom. Initially this was not as violent and ruthless as his fellow creatures: after his birth, in fact, he declared to the rest of his species that he wanted to create a collaborative bond with his host, taking from it only what is necessary to survive and giving him his knowledge. and abilities, while also leaving him in full control (contrary to his fellows, who subdued the host and completely deprived him of their life force, killing him). Precisely because of this anomalous way of behaving, the symbiote was considered mad and exiled to the Battleworld. When the Beyonder organized the secret wars he chose the very planet where the symbiote had been exiled as a battleground and, after Spider-Man ruined his costume, he was sent to a room where there was a machine to replicate it and inadvertently released the symbiote from the cage, which joined him as if it were a costume. The alien costume enhanced the physical faculties of Spider-Man, as well as giving him a resistance to the strenuous of invulnerability, a more effective healing factor, creating tentacles in case of need and knowing how to produce and cast cobwebs even without the help of his old web launchers, making Wall Climbing practically unbeatable. Happy with this discovery, Peter Parker wore it for the rest of the secret wars. After some time, Spider-Man returned to Earth, taking the symbiote with him, discovering other abilities of his, such as being able to replicate any clothing he wanted. Shortly after returning to his old life, Spider-Man had some adventures with the symbiote, and began to notice his overly "advanced" abilities and a change in his personality. Peter also began to feel tired all the time because unbeknownst to him the symbiote would take him for rides at night while Peter actually slept. Going to Reed Richards to have him examine the costume, they discovered that it was a living being who was merging his personality with that of Peter, exploiting his powers and starting to make decisions for him, even going so far as to be violent beyond measure; discovered the symbiote's aversion to intense sound waves, Peter then disposed of the costume / alien thanks to an ultrasound device by Richards, who then locked him in a glass bell. The symbiote still managed to escape by trying to reunite with its host, so it disguised itself as one of Peter's habitual customs and rejoined him. As a result of merging with Peter's mind, the symbiote is immune to the spider sense so it cannot be perceived.
After discovering the symbiont's deception, Peter started a fight with the alien and, heading towards the bell tower of a church, he exploited the tolling of the bells to remove the symbiote from himself permanently; Peter collapses lifeless, but as a last gesture of gratitude towards his host, the symbiote drags the unconscious body to safety and after having a final look, he leaves, aware that he has been rejected.
The alien remains a refugee in the church, where after a short time he met Eddie Brock, a journalist who hated Spider-Man to death because he accused him of ruining his life: Eddie intended to commit suicide, but the symbiote joined him and the his memories, finding in the hatred of Spider-Man a common purpose that allowed him to be completely accepted by the new host.