The Toxin symbiote's various hosts are former NYPD police officer Patrick Mulligan, Eddie Brock, and teenager Bren Waters.

His stressful job, along with the strain of his new family (his wife Gina was pregnant with their first son Edward) were taking their toll.

After Carnage attacked Gina and Edward at their home, Mulligan realized the Toxin symbiote was a danger to both himself and his family.

Spider-Man encouraged him, and Toxin resigned himself to a life of battling his base symbiote urges while trying to harness his power for good.

When Mulligan pressed the issue, it became clear that, unlike the Venom and Carnage symbiotes, Toxin is not sure it could survive on its own and find a new host.

[6] Mulligan is killed by Blackheart, resulting in the Toxin symbiote appearing in an underground lab in Las Vegas.

[8] Along with Venom, Anti-Venom, Hybrid and his sister Scorn, Toxin is mentioned as being the next option to stop Carnage's rampage in the Midwest after the Avengers are defeated.

[9] However, the US military is unable to find Toxin, leaving it up to the hybrid symbiotes and Scorn to stop Carnage.

[10] After killing Hybrid and Scream, Eddie Brock follows Venom into Crime Master's headquarters as part of his plan to destroy all symbiotes.

Toxin also seems to have some sort of quick-healing ability like his predecessors, as his wounds from his first battle with Razor Fist healed remarkably quickly.

The Toxin symbiote usually speaks when the host is in his "human form", and acts very immature and childlike because of its nascent existence, once refusing to aid Pat in battle until he apologized for an earlier argument.

When he is not angry or fighting, Toxin is slim and smooth-lined, although still well muscled, closely resembling Carnage or Spider-Man's symbiote costume.

When he becomes upset or aggressive, he grows into his much bigger and stronger form like Venom, with vicious fangs and long curving claws.