Plot
At the Teen Titans' base, Beast Boy finds an unusual crystal on the floor. The supervillain Control Freak then arrives, announcing that the Titans will have a new superhero crossover, so they all decide to watch the movie.
It depicts events from another universe, in which the Super Hero Girls fight against their enemies, the Super Villain Girls, who escape through a portal that opened behind them. This chain of events is related to Cythonna, the Kryptonian Goddess of Darkness, Plague, and Suffering, who was locked in an Amulet by her brother Rao and banished to space years before.
The Amulet was found by Lex Luthor, who used it to rescue the villains and form the Legion of Doom, planning to get rid of all superheroes by locking them in the Phantom Zone. The Legion wreaks havoc through Metropolis. The girls gather in the park and find a Kryptonian rune with Cythonna's name inscribed on it. Supergirl goes to her cousin Clark to translate it; he ignores her, believing that Cythonna is just a legend.
The girls head to the Fortress of Solitude to search for information about Cythonna and her Amulet, but they are confronted by Superman Robots, and then the League. A fight ensues, until Wonder Woman stops it and hands the crystals to Superman, deciding to leave the rescue plan in the hands of the League. Batgirl secretly steals the crystals, with the information they needed. Meanwhile, Wonder Woman receives a secret call from Batman, asking her to meet at the Daily Planet, where he and Superman tell her to join them to stop Luthor and the Legion.
Meanwhile, the girls watch a message from Supergirl's uncle Jor-El, who gave Clark a message about the Amulet. Cythonna plans to free herself from it by feeding on the souls of the wicked, use a Kryptonian vessel, and claim the universe as her domain. Deducing that Cythonna is controlling Luthor, the girls try to call Wonder Woman to warn the League, but she does not answer.
Meanwhile, as the crystal of the Amulet slowly shatters, she grows stronger. The League soon falls into a trap put on by the Legion.
Superman is locked in a Kryptonite box and the rest of the League is trapped in the Zone. Harley Quinn, having decide to quit the Legion and reunite with Batgirl, manages to help Wonder Woman escape. The girls dispute over the choices Wonder Woman made and dissolve the team. Out of guilt, Wonder Woman returns to her old home, Themyscira.
Luthor announces to the world that they will take over the world. Bumblebee sends an emergency call to her friends and encourages them to team up again. For her part, Harley leaves the girls behind, claiming that she is not interested in saving the world.
At Themyscira, the girls reconcile with Wonder Woman and return with her to Metropolis. There, the United Nations are forced to give the world to the Legion. Cythonna traps Supergirl, planning to use her as her new host. The other girls try to get to the Zone with the help of Zatanna's dark magic, which accidentally strands them in the Titans' dimension.
The Titans help the girls fix Bumblebee's computer and offer resources they need to return to their universe. Zatanna, meanwhile, receives words of encouragement from Raven that help her accept her dark entity. Zatanna transports herself and the girls to their own universe.
At the Zone, the girls rescue their friends, as Cythonna breaks free of the amulet. The girls, the Invinci-Bros, and the League subdue the Legion. Supergirl pretends to surrender to Cythonna, who is eventually overpowered by the girls. Supergirl imprisons Cythonna inside a crystal. Aided by Zatanna, she then banishes Cythonna out of her universe.
Meanwhile, on the Titans' universe, it is revealed that Cythonna is possessing Control Freak to retrieve the crystal. The Titans foil her attempt to destroy their universe, and she is banished by Raven, ending up stranded in another dimension. On that one, the Super Friends plan to send the crystal back, but take one look at the Titans fighting over the remote and decide not to.
