Aquaman won't have long to catch his breath after fighting alongside Batman, Wonder Woman, Flash and Cyborg in Justice League later this year. Next year, the water-based superhero will finally lead his own movie, and we already know about three individuals who will be giving him trouble in the story: Patrick Wilson's Ocean Master, Yahya Abdul-Mateen II's Black Manta and Dolph Lundgren's King Nereus. And these are just the ones we know about right now! Who knows, maybe sometime in the next year and a half or even during the movie itself, we'll discover one or more other nefarious figures.
He's almost certainly going to be the main antagonist. After all, you don't hire a guy like Patrick Wilson and reduce him to be a secondary or tertiary villain. More importantly, Aquaman has the most personal relationship with Ocean Master compared to his other adversaries due to their familial connection, i.e. a brotherly feud comparable to the dynamic Thor and Loki have in the Marvel Cinematic Universe. If Aquaman gets a sequel, hopefully Ocean Master isn't killed off in the first movie so we can see his relationship with Aquaman fleshed out, even if he doesn't retain main villain status.
Ocean Master's real identity is simply Orm. Following in the New 52's footsteps, the DCEU's Orm will share the same mother as Arthur Curry, Queen Atlanna, making him fully Atlantean. While we still don't know exactly what Aquaman's origins are in this cinematic universe, Temuera Morrison being cast as Thomas Curry suggests that like his comic book counterpart, Arthur Curry grew up with his human father on the surface. That, along with Momoa calling Patrick Wilson "King Orm" in an Instagram post, indicates that when we meet Orm in Aquaman, he'll already be ruling Atlantis. So rather than follow the traditional route of Orm trying to usurp the throne from Aquaman, our eponymous hero may be forced to overthrow his tyrannical half-brother, similar to what happened in the Throne of Atlantis arc.
Like his New 52 counterpart, Ocean Master has all the powers of an Atlantean, namely being able to breathe underwater and boasting enhanced strength. Along with these natural abilities, Orm wields a trident that can shoot magical lighting, as well as wears a helmet that allows him to manipulate water just like the Xebellians can (more on them later). Fortunately, Aquaman has his own special trident, so when they inevitably battle each other, it won't be an uneven match. As for weaknesses, Orm can't stay away from water for too long. He may be able to get away with being on the surface for days, but if he doesn't make contact with water, he'll start to lose his powers.
_Black Manta _is Aquaman's most notorious enemy. Introduced in 1967's Aquaman #35, he's a different kind of foil to Aquaman compared to Ocean Master, as Black Manta represents the worst that humanity can do under the sea. Black Manta is also responsible for a number of Aquaman's personal losses, which includes killing the hero's baby son. Fun fact, the animated series Justice League Unlimited used a character named Devil Ray who looked almost exactly like Black Manta, but they couldn't call him that because the rights were tied up with the live action Aquaman TV pilot, which didn't end up going to series.
Black Manta's real identity is David, with no last name ever officially provided. His origins vary depending on the DC continuity. In one version, the young David was kidnapped and forced to work on a ship, and subsequently hated Aquaman for not rescuing him. In another version, David was an autistic youth who only felt comfortable in cold water and was later subjected to cruel experiments at Arkham Asylum. In the New 52, Black Manta's hatred for Aquaman originated from an encounter where Black Manta and his father attacked Aquaman's father, Thomas Curry. In retaliation, Aquaman attempted to seek revenge on Black Manta, but ended up killing Black Manta's father by accident. Black Manta is also the father of Jackson Hyde, a.k.a Kaldur'ahm, the second Aqualad, who was first seen in Young Justice, introduced to the comics in the Brightest Day storyline and was re-introduced last year in the DC Rebirth relaunch. The irony that despite Black Manta's hatred of Aquaman, his son is one of the hero's most valuable allies, tastes so sweet.
Black Manta's abilities primary come from his deep-sea battle suit. Not only does that allow him to breathe underwater (duh), but it also has a number of weapons built in, including torpedoes, twin blades and energy beams that shoot out from the helmet's eyes. Even when he's not wearing the strength-enhancing suit, Black Manta is a skilled fighter, as well as extremely intelligent, but when fighting Aquaman, he understandably relies on technology more. Still, if that helmet comes off while Black Manta is underwater, he's screwed. Like any other human, he can only hold his breath for so long.
King Nereus may not actually be a full-fledged villain in Aquaman. When it was originally reported that Dolph Lundgren would appear in Aquaman, this version of Nereus is described as wanting to claim Mera as his own and kill Aquaman. Given that information, as well as the character's comic book history, it seemed like we could expect him to be a secondary or tertiary bad guy. However, director James Wan has since said that the DCEU's Nereus is "not quite" a villain. While we doubt that Nereus and Aquaman will be hanging out at an underwater beer to enjoy some sea brewskis, perhaps Aquaman will have to ally with Nereus so he can defeat Ocean Master and Black Manta.
King Nereus doesn't go by any other identity. He's proud to boast his royal title! Nereus is a relatively new addition to the DC Comics universe, debuting during Geoff Johns' New 52 Aquaman run. Nereus rules over Xebel, the underwater colony located in another dimension that is populated by Atlantean criminals and outcasts. Years ago, Nereus sent Mera to infiltrate Atlantean society to get close enough to Aquaman so she could kill him, but she ended up falling in love with the superhero. When Mera eventually returned to Xebel, Nereus had assumed that she'd finally come back because she'd accomplished her mission and was ready to become his queen. His assumption was wrong, so he received an invitation to become part of Aquaman's rogues gallery.
Just like the Atlanteans, King Nereus' main abilities are enhanced strength and breathing underwater. Additionally, like the other Xebellians, he can control water with his mind. Oh, and he has a spear...just in case. If Aquaman and Nereus battle in the 2018 movie, and assuming they don't head to the surface, then Aquaman will just have to overpower Nereus, but that'll be tough since the king of Xebel is also a formidable warrior.