It’s part of a secret history of Atlantis introduced in 2013 by writer Geoff Johns just before he left DC’s Aquaman. Aided by Mera and their allies, Aquaman defeated the Dead King and took back the crown. However, in the closing pages of Aquaman #25, King Nereus of Xebel sought out Aquaman’s brother Orm (aka Ocean Master) to pledge his loyalty and share the location of the Seven Seas, whose seven kings would once again rule the world.

From Aquaman #25 (2013)

Those revelations were intended by Johns to lay the groundwork for “Rise of the Seven Seas,” a planned crossover that would require the assistance of the Justice League. “It’s too big for him to handle alone,” Johns said, “so the Seven Seas, the seven members of the Justice League — it’s all going to be a nice, big story.” However, despite an announcement from Johns in November 2015 that he and artistic collaborators Ivan Reis and Joe Prado had begun work on the project, it’s yet to materialize. It’s entirely possible that Johns, DC Entertainment’s president and chief creative officer, borrowed some of those elements for the Aquaman film’s story, which he developed with Wan. The casting of Dolph Lundgren as King Nereus in the 2018 film may add credence to that. There’s also that matter of Graham McTavish’s “secret” role, which we could wildly speculate is that of Atlan, whether in flashback or as the Dead King returned for his throne.

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“Surpassing Justice League, this moment in time is his [Aquaman’s] call to become king,” Momoa said in that interview. “The only thing that can save Atlantis is me fighting my own brother. There’s a big battle, and there’s an epic [fight]. It’s also a big road movie, because we travel all over the world. It’s got that Star Wars quality of gigantic ships and guys riding sharks. It’s going to be this whole world you’ve never seen before. You’re going to see him start as this guy who probably rides bikes, works on cars. You get to see him this one way as kind of a dirty, dark, drunkard, and then turn into this regal king.”

The arc, as Momoa relates it, could foreseeably carry echoes of DC’s “Secret of the Seven Seas” storyline, only with Momoa’s Aquaman only ascending the throne after embracing his Atlantean heritage and coming to the aid of an undersea kingdom once again in peril. Whether that might be at the hands of Atlan, Nereus or simply Ocean Master and Black Manta remains to be seen.

Whatever the case, we can likely expect “Unite the Seven” to resurface soon, just not for Justice League 2.

Opening Friday nationwide, Justice League stars Ben Affleck as Batman, Gal Gadot as Wonder Woman, Henry Cavill as Superman, Amy Adams as Lois Lane, Jason Momoa as Aquaman, Ezra Miller as The Flash, Ray Fisher as Cyborg, Jeremy Irons as Alfred Pennyworth, Diane Lane as Martha Kent, Willem Dafoe as Nuidis Vulko, Ciarán Hinds as Steppenwolf, Jesse Eisenberg as Lex Luthor and J.K. Simmons as Commissioner Gordon.

Arriving Dec. 21, 2018, director Jame Wan’s Aquaman stars Jason Momoa as Aquaman/Arthur Curry, Willem Dafoe as Nuidis Vulko, Amber Heard as Mera, Patrick Wilson as Ocean Master, Yahya Abdul-Mateen II as Black Manta, Temuera Morrison as Thomas Curry, Dolph Lundgren as Nereus, Nicole Kidman as Atlanna, Ludi Lin as Murk, and Michael Beach as Jesse Kane.