UPDATE: Venom writer Donny Cates has officially confirmed our theory, so the spoiler effect is even more relevant, now!
WARNING: The following article contains spoilers for Venom #4 by Donny Cates, Ryan Stegman, JP Mayer, Frank Martin and Clayton Cowles, in stores now.
The space port known as Knowhere first appeared in 2008's Nova #4 by Dan Abnett, Andy Lanning and Wellinton Alves, a severed Celestial head floating at the edge of the known universe. More than just a hub, Knowhere is is a place alien races visit to conduct all manner of experiments in the hopes of uncovering the secrets of the universe. It's most famous for being the unofficial headquarters of the Guardians of the Galaxy, and is so closely associated with the team of space heroes, it's appeared in the Guardians of the Galaxy and Avengers: Infinity War films, where it served pretty much the same purpose it has in the comics.
Celestials are giant space beings as old as the cosmos itself, and this head has been floating for as long as anyone can remember. No one actually knows how it came to be here, or what had happened to the Celestial, but Venom, of all comics, might have just given us its secret origin.
Venom #4 is essentially a flashback issue that tells the origin of the series' main villain, Knull, aka the God of the Symbiotes. Knull lived in the darkness of space before there ever was light, and when the Big Bang came, the Celestials soon followed, looking to shape the new universe as they saw fit. Knull wasn't about to let them just run around smashing planets together, so he fought back. From his shadow, Knull pulled out a symbiote sword that would become All-Black, the Necrosword.
With this sword, Knull leaped towards the nearest Celestial, and sliced its head off. The rest of the Celestials cast Knull back to the deep blackness of space, but the entity found refuge inside his victim's severed head. There, he used the technology and the fires of the Celestial to mold the blade into the Necrosword. After that, Knull would leave the head, and move to spread the symbiotes throughout the Universe.
Though it's not stated outright, there's a pretty solid chance that this is how Knowhere was created. There might even be a hint in its name, which starts with the same two letters as Knull's moniker. The space port is so ancient that no one knows how it got there, and what could be more ancient than something that happened right after the birth of the universe, itself?
Of course, this is still merely a theory, as the story never explicitly states the severed head is the same one that eventually became Nowhere -- but we're going to stand by it for now. After all, Venom #4 rewrote everything fans knew about Venom, the Klyntar and the Necrosword; Knowhere could easily have been featured as an Easter egg origin story. And if that is the case, Venom's mythology isn't just tied to Thor, as we also learned it is in this issue -- it could also now be part of the Guardians of the Galaxy lore.