Trama

When a goddess of war reincarnates in the body of a young girl, street orphan Seiya discovers that he is destined to protect her and save the world. But only if he can face his own past and become a Knight of the Zodiac.

Produced by Toei Animation and based on the international anime sensation, Knights of the Zodiac brings the Saint Seiya saga to the big screen in live-action for the first time. Seiya (Mackenyu), a headstrong street teen, spends his time fighting for cash while he searches for his abducted sister. When one of his fights unwittingly taps into mystical powers he never knew he had, Seiya finds himself thrust into a world of warring saints, ancient magical training and a reincarnated goddess who needs his protection. If he's to survive, he will need to embrace his destiny and sacrifice everything to take his rightful place among the Knights of the Zodiac.—Sony Pictures

In days of Legends, Gods walked the Earth and tormented mortals. Athena, the Goddess of war ad wisdom had the power to destroy humanity, but she chose to protect them. Brave knights from across the globe swore their allegiance to her. They learned to harness Cosmo, the power of the stars. Over time, the gods retreated and became myths. But then, 18 years ago, Athena was reborn as a helpless child. A Knight clad in gold armor gave his life to protect her, as they crashed to the Earth. That is when Kido found her and since then has been for the new generation of Knights to protect and serve Athena.

Seiya (Mackenyu) is a street orphan searching for his sister Patricia, who had been kidnapped many years ago when they were both kids. During a fight with Cassios (Nick Stahl) in a fighting ring, Seiya unleashes a strange blue light. Post that Seiya easily beats Cassios but leaves before finishing the fight. After the fight, he meets with Docrates (TJ Storm) and Alman Kido (Sean Bean). Kido warns Seiya that his ex-wife Vander Guraad (Famke Janssen) is looking for him. Kido says that Guraad runs the fighting ring as her recruitment operation. She finds warriors with special skills for her private army. Guraad is looking for warriors with a strong Cosmo, and she just found one in Seiya.

Guraad's warriors capture Docrates and pursue Seiya and Kido, who meet up with Mylock (Mark Dacascos), Kido's assistant. Following a brief chase, Seiya, Mylock and Kido escape from the warriors. Seiya demands to know what is happening but is knocked out by Mylock. Seiya recalls his sister's kidnapping (Patricia asked Seiya to hide when Guraad's forces came looking for her) while unconscious and is later taken to Kido's hideout.

Kido informs Seiya that his adopted daughter Sienna (Madison Iseman) is the reincarnation of the goddess Athena, and Seiya is destined to become the Pegasus Knight, a warrior knight for Athena. Patricia knew about Seiya's destiny and gave herself up to protect him. Kido tells Seiya that he should train under Marin the Silver Knight (Caitlin Hutson), so that he can use his Cosmo to protect himself and Sienna, and to find Patricia.

While having breakfast with Seiya, Sienna briefly loses control of her Cosmo, but Kido is able to calm her down. Sienna reveals that Kido rescued her as a baby, but Guraad used the Gold Armor from the fallen Knight to develop technology way beyond man had ever see. Sienna tells Seiya that Cosmo are a window into the Universe, and learning to control them might help Seiya find his sister. Meanwhile, Guraad confronts Cassios for letting Seiya get away. Cassios beats up several of Guraad's powerful prototype soldiers and accepts an offer from Guraad to become one as well in exchange for exacting revenge on Seiya. Guraad wants to find and destroy Athena, before she becomes a Goddess and has the power to destroy the world.

Seiya and Sienna get to know each other, and she convinces him to go to Marin for training. Seiya goes with Mylock to the mountain where Marin resides and climbs up the mountain alone to meet with her. Marin specializes in helping Knights to control their Cosmo. Seiya's training initially goes poorly, as he is unable to channel his Cosmo properly, but he keeps training with Marin's help. That night, Sienna experiences a vision of herself as Athena destroying Seiya's armor and causing widespread global destruction, which causes her to emit another Cosmo burst.

Seiya eventually gains control of his Cosmo. His pendant glows and unlocks his Pegasus armor, but he experiences a vision while bonding with the armor, revealing that Kido was present when Guraad took Patricia. Seiya returns to Kido's hideout to confront him, but Sienna takes him away from the mansion. She reveals that she destroyed Guraad's arms when she was young, as Guraad was holding Sienna in her arms when her Cosmo activated. This forced Guraad to drain Cosmo from children with it to stay alive, and this is the reason why Kido helped Guraad kidnap Patricia. Guraad let Patricia go when she learned that Patricia did not have any Cosmo. But eventually Kido saw that Guraad was after power and not survival. Guraad was convinced that Athena had returned to the world to end it, and decided to kill Sienna and that's when Kido left it all behind.

Guraad arrives at Kido's hideout after her subordinate Nero (Diego Tinoco) tortures its location out of Docrates. Seiya and Sienna return to the mansion. Seiya fights off Guraad's soldiers, but he fails to activate his Pegasus armor while fighting Cassios, resulting in him being beaten unconscious. Kido sets his estate to self-destruct in an effort to stop Guraad, and he dies in the explosion. Sienna is knocked unconscious and captured by Guraad's soldiers, and Seiya is unable to stop them.

Guraad admits to Sienna that she has given up on fixing herself and proceeds to start depleting Sienna's Cosmo to prevent her becoming a threat to the world. Mylock rescues Seiya, who forgives himself for being unable to rescue Patricia when she was taken. Mylock and Seiya travel to Guraad's base, where Seiya unlocks his Pegasus armor and defeats Guraad's soldiers and Cassios.

Guraad becomes unable to watch Sienna be drained of her energy and tries to stop the procedure, but Nero turns against her and assumes his Phoenix Knight form. Nero and Seiya proceed to fight but are interrupted by Sienna (Guraad had reversed the process and returned all of Sienna's energy to her), who has almost completed her transformation into Athena, causing widespread destruction. With Seiya's help, Sienna manages to regain control, but falls unconscious afterwards.

When she wakes up, Sienna's hair has turned purple. Sienna and Guraad reconcile, and Sienna restores Guraad's arms. Sienna and Seiya leave the area with Mylock; Nero watches them leave. Sienna reveals that the old gods are returning, and the Knights of the Zodiac will be needed to stop them. She decides that they will need to find Patricia.