Aquaman and the Lost KingdomSave

Atlantis, several years after Aquaman (2018). Arthur Curry (Jason Momoa) is the official King of Atlantis. He has been married to Mera (Amber Heard, in a controversially reduced role due to her then-ongoing legal battle with Johnny Depp) and they have a newborn son, Arthur Jr. Arthur has been balancing his royal duties in Atlantis with his half-life in Amnesty Bay where his father Tom Curry (Temuera Morrison) still runs the lighthouse. Atlantis has been a UN-recognized hidden civilization for several years now. Arthur has been pushing to share Atlantean knowledge with the surface world to combat global climate change.

Black Manta. David Kane (Yahya Abdul-Mateen II), aka Black Manta, has spent the years since the first film's ending in covert research with Dr. Stephen Shin (Randall Park). They've been searching for ancient Atlantean weaponry. Manta has been driven by his vow of revenge against Arthur for not saving his father's life in the original Aquaman. His search has led them to Antarctica — where Shin's instruments have detected unusual seismic readings from beneath the Antarctic ice. Manta and a small mercenary team begin an Antarctic excavation.

The Black Trident. Beneath the Antarctic ice, Manta and Shin uncover a frozen ancient Atlantean artifact — the Black Trident, a counterpart to the King Atlan's golden Trident from the first film. The Black Trident is the weapon of Kordax, the brother of King Atlan, who tried to seize the throne of Atlantis ten thousand years ago. Kordax used the Black Trident's necromantic powers to attempt a forbidden reign of dark magic. He was defeated by his brother Atlan, who imprisoned Kordax in a small dimensional pocket called Necrus — the lost seventh Atlantean kingdom. Necrus has been hidden in the Antarctic ice for ten millennia. The Black Trident has been waiting for a worthy host. When Manta touches the Trident, Kordax's spirit possesses him through the weapon. Manta is now empowered by ancient Atlantean dark magic.

Possession. Black Manta's body changes. His skin develops a black-and-purple necromantic patina. His eyes glow red-orange. He has Kordax's memories, Kordax's combat instincts, and Kordax's plan: free Necrus from its dimensional prison and resurrect Kordax fully into Earth's reality. To do this, Manta needs to corrupt Atlantis's Orichalcum stockpiles. Orichalcum is the radioactive Atlantean fossil-fuel that has been powering Atlantis for ten thousand years. When burned at scale, Orichalcum releases a greenhouse-effect-amplification compound that would cause global atmospheric warming and dimensional-stability degradation. Kordax's full release requires Earth's atmosphere to warm to a specific threshold.

Manta's attack on Atlantis. Manta — now Kordax-Manta — leads a small mercenary force to Atlantis's central Orichalcum vault. Mera and Arthur's elite Atlantean defense force engage Manta's forces. Mera is wounded in the firefight protecting the vault. Manta extracts a stolen sample of weaponized Orichalcum and warps out via Trident-magic. Tom Curry's lighthouse in Amnesty Bay is also attacked by Manta's mercenaries as a diversion — Tom is wounded but survives. Arthur arrives back at the lighthouse to find his father bleeding.

Prison break for Orm. Arthur realizes he needs help from someone with deep Atlantean political knowledge. He pays a visit to his half-brother Orm Marius (Patrick Wilson), who has been imprisoned in a desert detention facility in the Sahara since the first film. Orm has been in solitary confinement for several years, drinking only a few liters of water per day (Atlanteans are functionally aquatic creatures and require water immersion to thrive). Orm is emaciated. Arthur breaks him out of the desert prison. Orm is reluctant — he is still bitter about Arthur's leniency in Aquaman's climax — but agrees to help locate Necrus.

The Sunken Citadel. The brothers travel to the Sunken Citadel, a small black-market underwater city ruled by the Kingfish (Martin Short, in a brief cameo as a small-time crime boss). Kingfish has been quietly trading in Atlantean smuggling for decades. He sells Arthur and Orm information about Manta's whereabouts — Manta has been operating from a secret Antarctic base where he is building a permanent Necrus-stabilization device. Arthur and Orm head south.

Antarctic showdown. Manta has been preparing his master plan. He has built an Orichalcum-burning facility at his Antarctic compound. He has been burning Orichalcum into the atmosphere for weeks, slowly warming Earth's climate to the Kordax-release threshold. Arthur and Orm arrive at the compound. They engage Manta's mercenaries. Black Manta — now fully possessed by Kordax — captures infant Arthur Jr. as a hostage to use as the spell's blood sacrifice (Kordax needs a royal Atlantean infant's blood to fully cross dimensions). Mera arrives via Atlantean reinforcements.

The brothers reconcile. Arthur and Orm, side by side in the final battle, finally reconcile. Orm has been the colder brother throughout. He admits Arthur's mercy in the first film had let him survive. He commits to redemption. The two brothers fight Manta-Kordax together. Mera rescues Arthur Jr. from the sacrificial altar. Arthur and Orm corner Kordax. Arthur uses King Atlan's golden Trident to channel Atlantean royal magic. Orm holds Manta in place via Atlantean warrior combat. Arthur shatters the Black Trident with the golden Trident, destroying both weapons simultaneously. Kordax's spirit is released back into the dimensional aperture and Necrus collapses fully into the Antarctic ice. The dimensional aperture closes. Kordax is gone.

Manta freed. Black Manta is freed from Kordax's possession. He's exhausted, broken, but alive. He no longer has the Trident's power. Arthur could kill him but spares him — Atlantean justice will hand him over to Atlantean prison. Manta is captured. Shin has been arrested. The Atlantean climate-degradation plan has been stopped.

Atlantis goes public. Arthur, in the aftermath of the Antarctic battle, makes a major decision. He travels to the United Nations in Vienna and addresses the assembled General Assembly. He officially announces Atlantis's existence to the world (which had been partly-confirmed before but never officially declared by Atlantean diplomatic representatives). He requests UN membership for Atlantis. He pledges Atlantean climate-mitigation technology to help the surface world combat global warming. The UN votes. Atlantis is granted full UN observer status. Arthur is now Atlantis's first diplomatic ambassador to the surface world.

Coda. Arthur, Mera, and infant Arthur Jr. return to Atlantis. Tom Curry recovers from his Amnesty Bay injuries. Orm is granted political asylum and reduced sentence — he'll serve out the remainder of his life on an Atlantean prison island rather than in solitary confinement. Black Manta is imprisoned permanently in an Atlantean detention facility. The film ends on a peaceful Atlantis sunrise scene with the Curry family on a balcony overlooking the underwater city. Arthur tells his father that he's proud of who he's become. Tom hugs Arthur. The DCEU has been officially closed out by the most-low-key superhero finale of the modern era.

Aftermath. The film grossed less than half of the original Aquaman's box office. James Gunn's DCU reboot has been formally announced. Jason Momoa has signed for the new Gunn-led DCU, with Momoa reportedly playing a different character (Lobo, the bounty hunter). The Aquaman DCEU has been retired. The Atlantis kingdom in the new James Gunn DCU will be re-introduced through different actors and different continuity. The film closes the Snyderverse-era DCU continuity formally and quietly.