WARNING: The following contains spoilers for King In Black #2 by Donny Cates, Ryan Stegman, JP Mayer, Frank Martin and VC's Clayton Cowles, on sale now.
The greatest threats to the safety of the Marvel Universe span all types of power, objective, and danger. With one of the most powerful threats to all of creation, Knull, having finally reached the Earth, it looks like it might be time for two current enemies to unite -- and unleash another powerful evil onto the world.
In King in Black #2, Namor and Iron Man just agreed to unleash the Black Tide to help fight back against the forces of Knull -- but that might just set up the next major threat to the Marvel Universe.
With Knull finally reaching Earth in King in Black, many Marvel heroes have already fallen to his influence and spread. There are only a handful of figures left who can rally against the forces of Knull, even extending to numerous current enemies of the Avengers and their allies. This includes Namor, who has been fighting the Avengers and setting himself up as a major enemy of the current Avengers. Despite his recent conflicts with the surface world, the coming of Knull and his symbiote army have forced the King of Atlantis to turn to his former allies in the Avengers for solutions. Unfortunately, this includes unleashing one of Namor's greatest weapons -- the mysterious Black Tide.
When Iron Man brings up that he knows about the Black Tide despite Namor's attempt to hide away their existence, Namor points out this is because the Black Tide is an incredibly dangerous element, and that sealing them away again will be incredibly difficult to achieve. But Iron Man replies that they really don't have a choice. If they want a world to fight with the Black Tide over at all, then they need to overcome the symbiote army that Knull brought with him. That requires every army they can muster, including the forces of Namor. This teases just how dangerous the mysterious Black Tide are. More info about the Black Tide will be explained in the upcoming Namor: King in Black miniseries by Kurt Busiek, Ben Dewey and Jonas Scharf.
The story focuses on Namor when he was a teenager before the events of World War II -- and how Namor, Lady Dorma and Attuma have to fight back against the encroaching Black Tide. While this might explain their origins, it's notable that awakening them for King in Black is still considered a major threshold by Namor. Even given his current violent impulses, Namor considers banishing the Black Tide away again will be "hell" -- hinting at just how dangerous the Black Tide really are to the future of the Marvel Universe. But Namor ultimately agrees to the plan, diving to the bottom of the Mariana Trench and confronting three mysterious figures in the waters.
On top of being a dangerous threat, the Black Tide appears to be more than capable of fighting through the inky blackness that Knull has brought to Earth. It also might be one way for Namor and the Avengers to mend the bridges that have been burnt between them, with Namor having the chance to call upon his former allies on the surface to help quell any threat posed by the Black Tide. But the question remains just how deadly the Black Tide are, and what about them could make Namor so wary to unleash them upon even something as dangerous as Knull.