WARNING: The following contains spoilers for Black Cat #2, by Jed MacKay, C.F. Villa, Brian Reber and Ferran Delgado, on sale now.
When Knull, the dark god of symbiotes, finally touched down in New York City with his vast symbiote army at the start of King in Black, he managed to defeat most of Earth's Mightiest Heroes in a matter of minutes. One hero that managed to avoid being transformed into a mindless recruit in Knull's army was Black Cat, who narrowly escaped after receiving one last mission from Captain America: Rescue Doctor Strange from Knull's clutches to help turn the tide of battle. As Felicia Hardy follows through on this task, she bonds with her own symbiote costume to rejoin the fight.
While reassembling her old crew to carry out the ultimate heist, one of Felicia's associates reveals they combined the Anti-Venom serum with some genetic modifications developed during the crossover event Absolute Carnage. With two containers holding the custom Anti-Venom symbiotes -- one for Felicia, one for Stephen Strange -- Black Cat leads her team to carry out the dangerous rescue mission. The master thief rides a drone before dropping on the captive Strange from above.
Anti-Venom was originally an alter ego for Eddie Brock introduced by Dan Slott and John Romita, Jr. in 2008's Amazing Spider-Man #569. Brock had intentionally separated himself from the Venom symbiote at the time. Instead, the classic Spider-Man villain Scorpion bonded to the symbiote and worked with Norman Osborn in the Thunderbolts. While Eddie was working at a soup kitchen run by Martin Li -- who was secretly the supervillain Mister Negative -- physical contact between Li's strange powers and the dormant symbiote cells in Eddie's body caused them to reactivate and mutate into a new symbiote known as Anti-Venom. The Anti-Venom sought to purge all symbiotes with his new cleansing powers. Eddie later sacrificed his Anti-Venom powers to restore the population of Manhattan from their sudden spider powers in the 2011 crossover event "Spider-Island."
Using one of the Anti-Venom devices to temporarily bond with the symbiote, Black Cat is able to enter Knull's prison where Strange is being held. Black Cat uses the remaining Anti-Venom device to free Strange and bond with him, with the two heroes escaping from the prison before the bonding process wears off and fleeing in Spider-Man's much-maligned vehicle the Spider-Mobile across the Manhattan cityscape.
Despite the overwhelming odds, Black Cat and her crew are able to rescue Doctor Strange from Knull's clutches. Though the Anti-Venom has been a formidable opponent for the symbiotes before, Black Cat's use of the modified symbiote seems to be a brief reappearance rather than the secret weapon to take down Knull. That said, Black Cat was able to use Anti-Venom to rescue the Sorcerer Supreme. If there is any one magical figure that could play a prominent role in saving the day, it's the Master of the Mystic Arts.