Namor the Sub-Mariner is back to being a villain again in The Avengers comic series, though interestingly enough the character is still a hero in the pages of X-Men: Red. The differing portrayals mean Marvel comics and movie fans are now in the same boat - completely unaware of what exactly Marvel wants to do with their king of Atlantis.
Having debuted in 1939, Namor is technically Marvel's first superhero. After being reinvented in the Silver Age of Comics by Stan Lee and Jack Kirby, the Avenging Son was revived as a villain, and a frequent foe of the Fantastic Four. Soon after, Namor received his own comic book series and was restored to his heroic roots. Since then, writers have occasionally used the character to fill the role of an antagonist, but for the most part Namor is portrayed as a hero. Namor has fought alongside the Avengers and the X-Men and is also a founding member of the Defenders - which makes it less and less clear why he's a non-player in Marvel's movie and TV plans.
At the end of Avengers #8, Namor renews his war on the human race, setting himself up to be the series' next big villain. Namor's actions appear to be inspired by the murders of several Atlanteans at the hands of the regular Marvel villains of the Roxxon Corporation. This will inevitably lead to a conflict with the Avengers, who are now led by the Black Panther. Since Black Panther and Namor are old enemies, it's unlikely that T'Challa will be able to talk him out of fighting.
What's confusing about this story arc is how Namor is currently being handled in X-Men: Red, where the character is a member of Jean Grey's new team, along with Gambit, X-23, Nightcrawler, and more. Namor agreed to help Jean Grey by letting her use Atlantis to establish a new mutant nation. In this comic, Namor's feud with humans is largely, when not completely ignored. At this point, it's unclear if X-Men: Red will address Namor's new direction in The Avengers, or vice versa.
Another interesting detail about Marvel's portrayal of Namor is the different designs used in his various appearances. In X-Men: Red, Namor has donned a green costume with the X-Men logo, while The Avengers has given Namor a new look. Both would make for fitting superhero costumes in a live-action adaptation, but in a recent issue of Thor, Namor was back in his classic green trunks. And to compound this confusion, Marvel's Defenders looks to represent Namor in not one, but both.
A lack of consistency makes it hard to say anything about Namor's future in Marvel Comics. His presence in multiple comic book titles shows that the Avenging Son is still a big part of the Marvel Universe, even if readers will have to undergo a few narrative bumps because he's in demand. The same can't be said for the MCU, which has yet to make use of the character, due to rights issues. Many are hoping that Namor will have a place in Marvel's Phase 4 - especially if the X-Men are retroactively added to the MCU.
Namor's rich history as both a hero and a villain would provide Marvel Studios with plenty of storytelling opportunities. Too many, in fact, if the comics are anything to go by.
Avengers #8 is on sale now from Marvel Comics.