After separating from Eddie Brock and laying low, Toxin is forced out of hiding during Knull's invasion and bonds with Bren Waters, the son of a Guardsman.
Bren debuts in King in Black: Planet of the Symbiotes #3 in a short story by Steve Orlando and Gerardo Sandoval. He bonded with Toxin before the beginning of the story. According to Toxin, Knull had no use for him.
Major Story Arcs
King in Black
After Toxin bonded with Bren, he thought of them as best friends, while Bren sarcastically referred to him as his "malignant passenger." Bren definitely seemed to enjoy the new power that Toxin afforded him and used it to become a superhero. While everyone else was battling Knull's symbiote army, Toxin and Bren took on a seemingly supercharged Brood, however, according to the Brood, he was a human who was experimented on by Alchemax.
Alchemax's involvement also means the Guardsman. A Guardsman got involved and fought Toxin for a chance to recover the Brood hybrid test subject, who just happened to be Bren's father, although neither Bren nor his father knew it at the time.
Bren was channel surfing with Toxin, when they uncovered a news story about a terrorist attack at Alchemax. It was actually a fight between Flash Thompson and Phage working on orders from Carnage. Bren is worried about his father, who works at Alchemax, so he suits up and heads there.
By the time he gets there, the fight is over, but he sees his father being wheeled out on a stretcher. His dad is still talking though and assures Bren everything is fine. Toxin, however, is not talking. He had been dragged into the symbiote hive-mind by Carnage, who was fighting him for control.
Thankfully, Toxin was able to defeat him and reconnect with Bren. After giving Carnage the boot, they can only sense one other symbiote, the newly created Silence, bonded to Andi. Those two were regrouping with Flash, who was assembling a team against Carnage, which Toxin accepted an invitation to.
With intel from Flash's friend Hank, who got a job with the Krane campaign, they learned the campaign planned to upstage the President's commemoration of those who died during Knull's invasion. Carnage intended to assassinate Sen. Krane, who was working for the Friends of Humanity. Bren and his new friends showed up to the demonstration to fight off The Life Foundation Five, until the Guardsman could take them into custody. Because Agony and Carnage got away, Flash and Andi reluctantly agree to let Bren stay in the loop despite his youth.