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.
After Knull arrived on Earth and took the planet over in shockingly little time, what little remained of the Avengers and the rest of the world's superheroes desperately tried to fight back in King in Black #2. Indeed, Tony Stark devised a plan to take control of a symbiote dragon, and have it merge with a severely wounded Eddie Brock to give them the upper hand against Knull. Thanks to his Extremis virus, Stark rewrote the dragon's DNA and bonded with it. The result? Iron Man now had a new symbiote armor to wield against the god of the void.
Now, in King in Black #3, the Armored Avenger joins the fight against Knull, and he shows just was exactly what his new symbiote armor is capable of by taking it to the ultimate, cosmic level.
For the first two issues of King in Black, the Avengers fought without their greatest asset against Knull: Thor. The god of thunder was missing for the villain's initial attack, but he arrives in issue #3 to smite the supervillain with all the lightning he can muster. The two cosmic powerhouses trade blows and, eventually, Thor smashes Knull in the face with his hammer, wounding him.
In answer, the villain furiously activates his dark Celestials, cosmic deities now consumed by symbiotes and controlled by Knull. These symbiote Celestials were unveiled in King in Black #1, only Knull barely had to use them to take over the world. But now that Thor is here, the villain sets them loose, and they unleash their cosmic power on the city around them.
As the Celestials fire devastating beams of energy on the ground, Iron Man arrives, flying atop his very own symbiote dragon. He explains that when Dylan Brock used his powers on the dragon in King in Black #2, it was freed from the symbiote hivemind, which means the creature now answers to him.
Therefore, Iron Man's symbiote armor is now an extension of his very own dragon, a conduit that gives him control of this massive and powerful symbiote. But as Tony reminds Reed Richards, it's not just a dragon: it's something that can be whatever he wants. He then commands the symbiote to take over one of the dark Celestials, with Tony inside. Essentially, Iron Man becomes the pilot of his very own Celestial, which allows him to fight the others with equal force.
This isn't actually the first time that Tony Stark has piloted a Celestial-sized armor in battle. Indeed, in 2018's Avengers #5, the genius billionaire unveiled the Godkiller Armor Mark II, which he used to battle the Final Host. Now, Tony has taken things even further by actually becoming the pilot of a Celestial. This symbiote suit allows Iron Man to become cosmic backup all on his own. With Thor now defeated, there currently aren't many superheroes left on Earth to fight back -- but the Armored Avenger is one of them.