Born from Carnage as the 1000th symbiote in its lineage, "Toxin" was feared to be the strongest and most dangerous of their race by both Carnage and Venom. Just born, the symbiote united with police officer Pat Mulligan.

Finding a group of kind hearted assortment of powered individuals, finding mentors in many aspects of their new life. Toxin learnt further what it was to be good. Sadly this new family passed and Patrick got a job as security protecting another larger organisation.

Years later, the symbiote was removed from Mulligan by Blackheart, who beat Pat Mulligan to death in a gutter, and contained in a secret lab in a casino in Las Vegas. With the help of Venom, Jack O'Lantern took it to his boss, Crime-Master. Crime-Master found the perfect host in Eddie Brock, whom he forced to become Toxin's host.

After bonding with Eddie, Toxin took over its host and worked with the Savage Six, attacking its grandfather symbiote, Venom. Toxin tells Venom that after Venom is gone only it will remain for an event it called the Spawning. The meaning of this is unknown, as of now. Venom managed to incapacitate Toxin, but chose not to kill it or its host. Later, Toxin attacked Venom and was separated from Eddie. Venom set the Toxin symbiote on fire, but it managed to recover its host and dragged him into the flames to die alongside it.

Both the symbiote and Eddie survived their attempted immolation and recovered from their injuries. Eddie and the Toxin symbiote worked out a truce to hunt down and kill Venom, after which they would try to kill each other, and began hunting down and killing numerous criminals and gang members. Toxin eventually tracked Venom down to Philadelphia and tried to kill him, but Flash's speech to Eddie caused him to call off his vendetta and accept his bond with Toxin, using it to return to his Lethal Protector lifestyle. Following Eddie's arrest by the FBI, the Toxin symbiote was suppressed using symbiote inhibitor drugs, and is only capable of taking action if injected with the antidote.

In order to empower her to fight Carnage and Chthon, Eddie Brock gave the Toxin symbiote to Jubulile van Scotter, who combined it with her own symbiote and the Raze symbiote. The amalgamated symbiote dispersed into wisps of golden light after being used to slay Chthon, seemingly marking the death of all three.

Not known even to Brock but Toxin's pieces left behind in the friends he had made in his time mixing with other powered beings. Here is where he would grow once more and reform. Having reformed from tiny pieces across his friends Toxin has now taken to a dog which was the nearest living thing at the time that he didn't feel bad piggy backing on.

http://marvel.wikia.com/wiki/Toxin_(Klyntar)_(Earth-616)

https://www.youtube.com/watch?v=DwJn4SE9Uu8