The Hive was the name used by the Poisons, a group of interdimensional creatures who can assimilate Klyntar and consume their hosts to gain their likeness, memories, powers, and abilities. The Hive's Poisons were controlled by the Poison Queen, who was empowered by the life-force of those consumed and could speak and act through them. However, the Poison Queen's control was not absolute as several individuals resisted being consumed and/or rebelled against the Hive - namely Poison Deadpool, Poison Marvel Girl, and Poison Carnage.
The Hive was first encountered when Doctor Strange stumbled upon a symbiote on the run from the Poisons. In an attempt to stop the Hive's Multiversal quest for dominion, Strange summoned other Venomized heroes, villains, and antiheroes to form a Resistance. Unfortunately, many members of the Resistance were assimilated into the Hive.
Strange eventually summoned the Venom of the Prime Marvel Universe to aid the Resistance, losing both Venomized Spider-Man and Captain Venom to the Hive.
Meanwhile, the Hive also explored other avenues to conquer the Multiverse. One such attack was carried out by Poison Fin Fang Foom, who managed to access the mind of the Kid Kaiju from the Prime Marvel Universe, forcing the boy to summon him to that Earth's Savage Land. Kid Kaiju's monsters were summoned to defeat this Poison, but were unable to do so because Kid Kaiju doubted himself, thus weakening their abilities. This prompted Kid Kaiju to summon the Fin Fang Foom of the Prime Marvel Universe to defeat the 'impostor' and, while Foom was initially defeated in combat, he managed to give Kid Kaiju enough self confidence that his monsters could regroup and kill the Poison.
Back in the Venomverse, Venompool willingly joined the Hive, believing that his strong personality and healing factor would allow him to survive the assimilation. This infiltration succeeded and the Resistance gained a mole in the form of Poison Deadpool. Poison Deadpool "captured" Carnage, enabling the remaining members of the Resistance to mount a rescue in which they saved Strange and killed most of the Poisons based in Earth-22249.
After the failed attempt to use Kid Kaiju, the Hive fullfilled succeeded in their objective of travelling to Earth-616. Once in this univese, the Hive used the services of Symbiote-hunter Haze Mancer to raid Klyntar, the homeworld of the Symbiotes, and abducted all of its inhabitants. In the process, the Poisons stumbled upon the X-Men and Venom, who were in a space adventure, and assimilated Jean Grey.
The Symbiotes kidnapped from Klyntar were genetically modified so it would be harder to separate them from their hosts. The Hive then traveled to Earth, and started forcing the Symbiotes they abducted to bond with numerous superhumans, so they could be consumed in turn. The Hive additionally deployed agents to capture this world's Carnage, since they expected him to be a threat. Since Kasady had been stripped of his Symbiote, the Hive was able to trick him into bonding with another and then assimilating him.
Jean Grey's psyche had survived the assimilation due to her powers, and she called out for Cyclops, allowing the heroes to learn the location of the Hive's mothership. Only Venom, the X-Men, Spider-Man and Daredevil made it to the mothership, since a Quinjet transporting other heroes was taken down from the sky by the Poison Thanos. When they encountered the Poison Queen, who was using Poison Marvel Girl's powers to bolster her own, Jean Grey killed Poison Marvel Girl from within before killing the Poison Queen and reconstituting her body. Since all members of the Hive were connected to the Poison Queen, her death caused a chain reaction that destroyed almost every single Poison, assimilated or unbound. The only known Poisons to have survived were one that had assimilated Jimmy Hudson and Poison Carnage, though the latter had mostly retained his original psyche.
Very few of the assimilated Poisons originated from the Hive's native universe. Poison Thanos might be the only one.