The creature that would ultimately become Venom was born to a race of extraterrestrial parasites, which lived by possessing the bodies of other lifeforms. The parasites would endow their victims with enhanced physical abilities, at the cost of fatally draining them of adrenaline.
According to the Planet Of The Symbiotes storyline, the Venom symbiote was deemed insane by its own race after it was discovered that it desired to commit to its host rather than use it up. The symbiote was then imprisoned on Battleworld to ensure it didn't pollute the species' gene pool.
Life and Powers
The Venom Symbiote gives each of its hosts a slightly different appearance in their Venom forms, though each is relatively similar. Initially when Venom first formed with Eddie Brock the creature was portrayed as black, considerably taller and much more muscular than Spider-Man. Over the years however, the general design of Venom has altered, even with the same host. Its eyes resembled those of the Spider-Man suit but larger and more "evil" in appearance. Its trademark was a wide grin which displayed all of his teeth.
In his most famous incarnation he developed a long tongue, he also started being drawn as blue or blue-black as opposed to the original black. His eyes became more menacing and "alien" like, while his size increased to that which would be extremely difficult for Brock to obtain through even his most rigorous weight lifting. Also the spider symbol on its chest has been known to change appearance, which the symbol of the back and front connected or not. John Romita Jr's design had Venom much leaner with abnormally long fingers. Mike Deodato's recent design of the Mac Gargan Venom has normal-human eyes within large white patches resembling Venom's traditional Spider-Man like eyes. The Gargan Venom has also been drawn as purple, much like the Venom in Ultimate Spider-Man. Though it requires a living host in order to survive, the Venom symbiote has been shown on some occasions to be able to fend for itself with its own set of unique powers. The symbiote, without a host, has shown shape-shifting abilities like forming spikes and expanding its size.
The symbiote is telepathic and does not require physical contact to influence the minds of others. In Planet Of The Symbiotes, the creature, after being rejected by its host, emits a psychic scream which drives nearby humans to states of extreme depression. Later, with the assistance of Eddie Brock, it emits an even more powerful variant of that power which results in the mass suicide of an invasive force of symbiotes. The symbiote can also blend with any background, using an optic-camouflage type of effect. Venom is immune to the Penance Stare, an ability used by Ghost Rider Johnny Blaze and Daniel Ketch.
The symbiote originally rejected its species habit of consuming its hosts, but still required certain chemicals (human adrenaline) in order to survive. When starved of these chemicals, the symbiote developed a mutable exoskeleton, allowing it to form its own solid body which it use to hunt and kill prey without the assistance of a host.  It was revealed in "Venom: The Hunger" that the suit used Eddie Brock's cancer as food because it produced a kind of substitute adrenaline, but left him because his cancer would soon be proving fatal. After failing to attach to Spider-Man, it temporarily reattached itself to Eddie. Later the suit's evolution progressed and as shown in the 2003 Venom comic book series, it could spontaneously jump from host to host and killed them after every departure from said hosts
These creatures had cloned Venom in order to fulfill their objective: extermination of the human race. The clone would burn out its hosts' life, unlike the real Venom (traits which seem to be a throwback to the invading symbiotes seen in Planet of the Symbiotes). Bob had the clone released and it caused the slaughter of the outpost.
The Venom clone hitched a ride on the survivor back to base, despite the best efforts of Robertson and her new ally. The mysterious Suit was made of the same robots as Bob, which was revealed to have been unwittingly brought to Earth by Reed Richards and made into a special agent by Nick Fury. It is unclear if the Suit's loyalties lie with Nick Fury or Bob, if either. Meanwhile, the genetically altered symbiote killed all of Patricia's friends and coworkers. While Robertson was unconscious, the Suit cybernetically altered her, shaving her head, attaching a metal pipe in it, and placing a control collar on her so that in case the symbiote clone bonded with her she could control it. Meanwhile, Ararat Co. and the spider-robots nuked Voici, Canada leaving the symbiote with few options. After the Suit sabotaged the symbiote's favored host, Wolverine, it was forced to jump to the last surviving potential host, Robertson.
One of Bob’s agents, disguised as the Suit, told Robertson that she had to kill the real Venom or the symbiotes would destroy all of humanity. Attempting to get to Venom, she freed him from S.H.I.E.L.D. custody. Their first fight was broken up by the real Suit, and the electrocuted Venom retreated. The Suit chided Robertson for coming to New York due to there being many people in the city and all of the population could be in danger if the symbiote clone jumped hosts.
Meanwhile, Bob remotely deactivated Patricia's control collar so that nothing restrained the symbiote but Patricia's willpower. Robertson continued trying to kill Venom, beating up Spider-Man when he got in the way. She was captured by the Fantastic Four, who used her as bait to lure Venom into a trap. Unfortunately, Spider-Man’s interference and the strength and craftiness of Venom caused the trap to fail. Fighting again, Venom absorbed Robertson’s symbiote clone, as Bob hoped, and increased in size and decided to carry out the Ararat Corporation's goals. Patricia's fate is uncertain, and the entire plot has gone unresolved.