Law-abiding citizens begin to murder people, believing their victims to be demonic creatures. The Justice League concludes that magic is the source of the crimes, but Batman is skeptical. Later that night at Wayne Manor, he finds a written message on his walls: "Constantine".
Five days prior, occult detectiveJohn Constantine and Jason Blood engage the Demons Three in a high-stakes poker game. Constantine offers his home, the House of Mystery, in exchange for a box of artifacts, including a chipped Dreamstone. When both parties are caught cheating, Constantine magically forces Blood to summon Etrigan to dispatch the demons. Afterward, Blood reprimands Constantine and the two part ways.
In the present, Batman seeks out Zatanna to find Constantine. They are joined by Deadman, and the two lead Bruce to the House of Mystery, where they meet Constantine; Constantine reluctantly agrees to help investigate the supernatural occurrences. The team then visits Ritchie Simpson, a collector of magic relics and old friend of Constantine and Zatanna. Ritchie, who has a magical form of cancer, is resentful of Constantine for abandoning him to his current predicament, but loans them the Keshanti Key, which Constantine and Zatanna use to view one of the victim's memories. However, a mysterious figure summons a creature to consume the victim and cover up the crime. Constantine and Zatanna manage to find how the victim was possessed and narrowly escape, with Constantine retrieving the image of a ring the spirit was wearing.
They return to Ritchie's to identify the ring, but find him close to death with Blood standing over him. Constantine pursues and captures Blood while Batman administers adrenaline to revitalize Ritchie. They take Ritchie and Blood back to the House of Mystery, and Constantine charges Black Orchid, the House's spiritual embodiment, with tending to Ritchie while the rest interrogate Blood. Blood explains that he sought to access the House of Mystery and retrieve the Dreamstone, and found Ritchie dying at the scene. He reveals that, centuries ago, the sorcerer Destiny created the Dreamstone in an attempt to overthrow Camelot, forcing people to see their worst nightmares and feeding off their torment. Blood was mortally injured in the battle, prompting Merlin to summon Etrigan to defeat Destiny, whose soul was imprisoned in the Dreamstone. After the battle, Merlin bound the dying Blood and Etrigan together, knowing that they would be needed in the future.
Ritchie briefly wakes and claims Felix Faust was his assailant. With Swamp Thing's help, the group locates Faust's observatory, defeating him in battle and concluding that he is innocent. Ritchie awakens and is revealed to have the other piece of the Dreamstone, which has been keeping his cancer in remission; he takes over the House and forces Black Orchid to burn her own body to ash. Constantine tries to convince Ritchie that Destiny is manipulating him, but Destiny uses the Dreamstone to take control of his body.
Destiny destroys the House and departs; Zatanna saves the group, but passes out from exertion. The Justice League tries to fight Destiny, but his magic forces them to turn on each other. Etrigan attacks, but is separated from Blood. Constantine summons Swamp Thing, who engages Destiny while Batman and Zatanna subdue the League. Destiny rips Alec Holland's corpse from Swamp Thing, breaking his will and forcing him to withdraw. Constantine tricks Destiny into bringing him and Deadman within his shield, allowing Deadman to control Destiny long enough for Blood to fatally wound him with Etrigan's sword. Constantine and Batman destroy the Dreamstone, bringing back Ritchie, who is dragged to Hell for his sins, ensuring that Destiny cannot come back. Blood succumbs to his original wounds, and is buried near the site of his old village. Zatanna, having agreed to join the League, offers Constantine a position as well. He declines, claiming that Batman would not approve, but Zatanna states it was Batman's idea. The two return to the reconstructed House of Mystery to discuss their League applications, and Deadman joins the restored Black Orchid as her soulmate.
Dave Trumbore from Collider wrote: "Justice League Dark is a briskly paced, darkly magic adventure that gives some of DC's most shadowy heroes a chance to shine in a story that folds in mythology and mystery, while never losing sight of what it means to be a hero". Felix Vasquez Jr. of Cinema Craze also praised the film, calling it a "fun celebration of supernatural elements in DC comics".[3]
It earned $3,325,752 from domestic home video sales.[4]
The film spawned a spin-off animated web series titled Constantine: City of Demons that was released on The CW's online streaming platform CW Seed on March 24, 2018, with Ryan reprising his role. It was originally made to be a sequel to the live-action series Constantine and a part of the Arrowverse franchise, but writer J. M. DeMatteis stated that the direction of this series was changed and that it was set in the DC Animated Movie Universe.[5]
