The beings now known on Earth simply as "symbiotes" are a conquering, predatory race of amorphous aliens that bond to a host and parasitically feed off their emotions and bodies. They tend to force their hosts to perform spectacular and terrifying feats in order to feed off of the resulting rush of adrenaline (and possibly other hormones, such as phenethylamine). Eventually, these host beings would be sucked dry, exhausted by the constant stress and exertion, or simply die in a failed stunt. Symbiotes are fully aware and sentient creatures, but are also vicious and wild, compelling their hosts to violence. Several symbiotes, such as Venom, Carnage, Toxin, and Zzxz, have developed appetites for the flesh of other life-forms and will influence or force their hosts into committing cannibalism. They are much more effective if the host has the same feelings and urges as the symbiote. For example, the Venom symbiote bonded successfully with Eddie Brock because they shared anger and desires for revenge towards Spider-Man. As this shows, symbiotes are able to project their own emotions and personal desires, in addition to reflecting and reacting to the emotions and desires of their host, to the point of assuming complete control over their host's body if they so choose. A symbiote's influence over its host can be resisted and suppressed through a number of means, including willpower and chemical sedatives.
The symbiote that would eventually become Venom was identified as deranged by others of its race because it sought to form a single, strong, symbiotic bond with its host, rather than using them as chattel. In fact, it is because of this creature that humans initially believed the entire race to be symbiotic. This symbiote would later describe itself as a mutant among its species. The symbiote was placed in a prison canister, and supposedly condemned to death by disintegration.
During the Secret Wars, when several of Earth's heroes and villains were transported to Battleworld by theBeyonder, Spider-Man went looking for the alien technology Thor had stumbled upon to repair his tattered costume. Instead, he found the machine holding the symbiote captive. The released symbiote did indeed form a "costume" for Spider-Man -- as the race naturally covers their entire host -- and responded to Parker's thoughts by patterning itself after the new Spider-Woman's black and white costume.
The new "costume" had several useful properties -- the ability to mimic other forms of clothing, a "dimensional aperture" which could store small objects without adding bulk to the costume, and its own source of webbing -- which Spider-Man initially attributed to its alien origins. After returning to Earth, the costume could not stand to be separated from Parker for very long, and it often engulfed the sleeping hero, sending him out to fight crime under its control. The then-villainous Puma -- who was fighting Spider-Man at the time -- was the first to perceive that the costume's webbing was organic, causing the hero to seek the advice of Reed Richards. Richards isolated the living costume, setting into motion a series of events that would lead to the creation of Venom -- the merger of the symbiote and Spider-Man critic Eddie Brock.
Venom proved to be a particularly malicious foe, and broke several laws in pursuit of revenge against Spider-Man. On one occasion, while Brock was incarcerated for his crimes as Venom -- and while he patiently waited for the escaped symbiote to free him -- he shared a cell with multiple-murderer Cletus Kasady. The symbiote did in fact liberate Brock, but in so doing left behind its spawn. The symbiote spawn bonded with Kasady, turning him into the lethal villain Carnage (Cletus Kasady). Because Kasady bonded with the symbiote on a cellular level(something Brock refused to do) Carnage proved more formidable than either Venom or Spider-Man, and the two eventually formed an uneasy alliance to deal with the threat. The Carnage symbiote was capable of greater control of its constituent matter than the Venom symbiote. At one point, it managed to travel by telephone line by thinning itself to a strand of cellular width. It could also form solid appendages, allowing Carnage to form spikes, blades, and axe heads at will, though the Venom symbiote recently developed this ability as well. The symbiote appears to be more dense as well, allowing its host to become more durable and stronger than the Venom symbiote would allow.
At one point, Venom was captured by the Life Foundation, an organization that made a comfortable living in preparing for the world's nuclear annihilation. Convinced that a nuclear war was inevitable, the Life Foundation's clients payed to assure that the human race (and they in particular) would survive the cataclysm in luxury. The Life Foundation was at one point researching a way to create "super-cops" to police their new Utopia. Towards that end, they probed the Venom symbiote and extracted the last five of its "seeds" -- the basis for later spawn as the symbiotes reproduce asexually. These were cultured and bonded to five of the Life Foundation's best security personnel to form the Guardians. The individuals eventually became known by the codenames Scream, Riot, Phage, Agony, andLasher. Either due to the extraction process, the effect of the Earth environment on the spawn, or both, these symbiotes proved to be even more mutated than Carnage. They possessed the same ability to manipulate their forms as Carnage. However, the five never quite got the hang of actually communicating with the under-developed symbiotes.
After several crushing defeats, Scream had a psychotic breakdown (possibly contributed to by her schizophrenia,) and determined that all symbiotes were evil. She killed off her former compatriots with a sonic blade, not realizing that the symbiotes themselves had survived. The four symbiotes were kept for a time in the Vault high-security prison for super-beings, but were freed from the lab by Guardsmen Scott Washington, who decided that they were not evil and did not deserve a lifetime of pain and suffering. Washington was fired when it was discovered that he had freed the symbiotes. All four symbiotes were weak, and survived by bonding together to form a single, more powerful being. This symbiote later went on to merge with Washington, who had been crippled after a scuffle with the Eazy X gang following his return to the Bedford-Stuyvesant section of Brooklyn. After bonding with the hybrid symbiotes, he regained use of his legs, and began extracting revenge on the gangs that had destroyed his neighborhood as the crimefighter "Hybrid".
Spider-Man led Brock to doubt the nature of his relationship with his symbiote, suggesting that it had been controlling him. When Brock ordered the symbiote to separate from him so that he could consider the matter, the pained symbiote let out a "psychic scream" of anguish so powerful that it drew others of its kind from space. Using a unwilling innocent as its host, the Venom symbiote and the extraterrestrial symbiotes constructed a portal to an alien world, the native population of which had been enthralled by the symbiotes. The symbiotes then launched a full-scale invasion of Earth, starting in New York. In the ensuing chaos, Carnage found that she could absorb the symbiotes to increase her symbiote's mass and power, and temporarily became monolithic in size by doing so. Brock realized that the creatures were highly sensitive to emotion, and (with his now-penitent symbiote) released a wail of anguish so great that it was able to kill most of the symbiotes.
Soon after, the presence of the surviving symbiotes attracted their only known predator, the Xenophage. Xenophages are a race of amorphous, shape-shifting aliens whose diets consist mainly of symbiotes, though they are not above eating the occasional humanoid if they get particularly hungry. The Xenophage took a particular interest in Venom, as symbiotes tend to become more "flavorful" after bonding with a host for a long period of time. Venom managed to dispatch the first Xenophage, though more eventually arrived on Earth to seek out their exotic prey.
Much later, Carnage realized he was also about to spawn. Fearing the spawn would become more powerful than him and disgusted by the notion of reproduction, he resolved to destroy the spawn as soon as it was born. Venom also became aware of the spawn, however, and resolved to protect it and culture it as an ally. After the new symbiote was spawned, Carnage was too weak to kill the creature himself, and the symbiote found a human host in officer Patrick Mulligan. Venom had warned Carnage that every thousand generations or so the symbiotes' genetic memory can break down, and the new symbiote must be instructed by its "grandparent" to correct the errors. Since Venom has not been able to do so, this new symbiote bothers the unfortunate cop with the numerous questions, quandaries, and tantrums that normal children experience as they age. The difference, of course, is that normal children tend to have fewer urges toward homicide. Mulligan is currently doing his best in balancing work, his family life, the difficult new symbiote, and his new career as the crimefighter "Toxin". Mulligan was later murdered by Blackheart, who took the symbiote and bonded samples of it to clones of X-23. The Toxin symbiote was subsequently stolen by the Crime Master and bonded to Eddie Brock. Despite initially seizing control of him, the Toxin symbiote and Eddie have since worked out a similar relationship to the one Eddie once had with Venom.
Eddie Brock, disgusted by the symbiote's growing bloodlust after having a religious awakening and fearing for the fate of his soul, sold the symbiote toDon Fortunato, who gave it to his son Angelo. The symbiote abandoned Angelo of its own accord and later sought out Mac Gargan, influencing him to commit cannibalism to satiate its hunger. After the events of Brand New Day, Eddie Brock started working for Martin Li and Aunt May at the F.E.A.S.T. center. Thanks to Mr. Li's "mysterious powers." Eddie was cured of his cancer and the remnants of the symbiote were fused to his white blood cells. Unfortunately, the current Venom entered the F.E.A.S.T. center looking for Spider-Man. He found Eddie and the symbiote began to crawl onto him again. However, the mystically-enhanced fusion between the symbiote's cells and Eddie's lymphocytes emerged, forming Anti-Venom. Eddie later sacrificed the Anti-Venom symbiote to create a vaccine for the Spider-Virus, but it appears a portion of it was somehow acquired by the Hobgoblin, who enfranchised the identity as one of his "Hob-Heroes" after his Inversion.
Later, when Carnage returned Earth after her apparent death, Hall Industries used the symbiote to produce advanced prosthesis, one Dr. Tanis Nieves used, resulted to be a new spawn, how bonded her transforming them into Scorn a machine/symbiote hybrid, who tries to stop Carnage.
Following its separation from Mac Gargan, the Venom symbiote was given to Eugene "Flash Thompson by the US military, having been administered a sedative to keep it from seizing control of him. Flash later allowed the symbiote to bond to him, and it expressed a preference for him as a host, despite attempting to return to Eddie Brock and later "Peter Parker". When not suppressed the symbiote tends to rampage and attempt to eat any nearby enemies, and later exhibited a desire to acquire demonic powers: bargaining with Mephisto to receive a Hell Mark and attempting to absorbZarathos during the Circle of Four, but was forced to relinquish those powers to its clone, Mania, after a demon implanted in it by Daimon Hellstrom began attempting to take it over. During Flash's sojourn into space as a member of the Guardians of the Galaxy, the Venom symbiote became increasingly erratic, eventually seizing control of him and rampaging until they were separated, whereupon it took control ofGroot.
Another symbiote, unrelated to Venom's lineage, was captured by ShiarEmperor D'Ken and given the moniker Zzxz. Classified as one of the most dangerous entities the Empire had encountered, it was recruited by Vulcan to serve as one of his praetorian guards and eventually took Raza Longknife as a host. Zzxz was later separated from Raza and imprisoned on Ego.
In Earth-1610, the symbiote is a proto-plasmic suit developed as a medical cure for cancer by Richard Parkerand Edward Brock Sr. The suit was unfinished and stolen by Bolivar Trask. Edward Brock Sr., however, managed to saved a small sample of the symbiote for his son, Edward Brock Jr., to find.
In Larval Earth, the Symbiote is not identified as such: The Bee-Yonder suddenly appeared in front of Spider-Ham and used his powers to change his red-and-blue uniform into a black-and-white one; giving no other explanation, the Bee-Yonder, apparently a fashion consultant, teleported away to change the style of Ducktor Doom's ensemble. Spider-Ham, who liked his original suit, returned to the red-and-blue uniform after this encounter, Later, during the event known as Secret Furs, Spider-Ham was seen using a different black-and-white uniform while fighting Doctor Octopussycat for a refrigerator in Bobcat Barker's "Whale of Fortune" test.