WARNING: The following contains spoilers for King in Black #3, by Donny Cates, Ryan Stegman, JP Mayer, Frank Martin, and VC's Clayton Cowles, on sale now.
While the heroes of the Marvel Universe put up a valiant defense when the planet was targeted by the villainous Knull and his army of symbiotes, there was one glaring absence among Earth's Mightiest Heroes in the first battle of the crossover event King in Black. Thor was nowhere to be found, with his teammates on the Avengers unsure of his whereabouts or how to contact him for help. And just as all hope seems lost and the Earth is poised to fall to the dark god of symbiotes, Thor finally makes his grand entrance in an effort to turn the tide of battle in King in Black #3.
However, this particular clash of titans finds the God of Thunder quickly put on the defensive as Knull recalls that his symbiotes have bested the Asgardian Avenger before.
Even before recent events, Thor was always one of the Avengers best suited to take on Knull head-on. As the Asgardian God of Thunder, Thor's mastery over lightning and his mythical weapon Mjolnir seemed perfect to combat the vast symbiote hordes, given their natural weaknesses to electricity and magic. Following the crossover event War of the Realms, Thor was crowned King of Asgard, effectively inheriting the powers of the All-Father from Odin to become the most powerful warrior in all of the otherworldly realm. And to up the ante further, Thor recently served as a Herald of Galactus, taking on the Power Cosmic, ultimately using it to destroy Galactus himself and drive back a destructive entity known as the Black Winter.
Thor has had some experience, of course, battling against symbiotes, with a flashback in 2018's Venom #4 set centuries into the past showing a significantly younger Thor battling Knull's monster Grendel on Earth. After an epic battle, Thor used his lightning to sever Knull's mental control over the Klyntar symbiotes long enough for them to gain self-awareness and force the villain into a lengthy hibernation. More recently, Thor and Galactus faced off against the destructive villain Black Winter, with the cosmic entity revealed to have been Galan's former master and implying he and his powers may be linked to Knull just like the God Butcher Gorr.
Given the telepathic connection Knull holds over his symbiotes, the dark god recognizes Thor after seeing his divine powers in action, just as one of Knull's symbiotes had in Venom #21. Thor puts up more of struggle against Knull than any of his prior opponents, including Venom himself, striking at him with his magical lightning and driving him back from Dylan Brock to keep the young boy from the villain's grasp. Undeterred, Knull calls in his venomized Celestials as cosmic reinforcements while brutally eviscerating Thor while the God of Thunder's attention is called away, effectively retaking control of the fight in a few, short moments.
Thor is still alive and ostensibly still in the fight but the Asgardian's opening onslaught has been stopped dead in its tracks as Knull reasserts himself. After a conspicuous absence at the start of King in Black, Thor is officially in the thick of the crossover event but, even with all his new tricks and toys, still comes up just short of defeating Knull and his armies for good. Through his symbiotes, Knull is familiar with the God of Thunder and has mounted an effective counterattack that has left Thor bloodied and beaten as King of Black continues to escalate its conflict for the fate of the Marvel Universe.