The Seven Deadly Sins: Cursed by Light

Fairies and giants attack the wedding because they have been under the control of Dahlia, a powerful fairy, and Dubs, the Giant Master Craftsman. These two have taken over the Demon World and are using enchanted weapons to force the fairies and giants into attacking the Sins and their allies as punishment for defeating the Demon King.

Earlier, a dying demon revealed that the Demon World had been overrun by a fairy and a giant, hinting at the source of the coordinated attacks.

The Supreme Deity attacks because she views the Sins as a threat, even though they defeated the Demon King. She intends to destroy them to end the Holy War entirely, believing the Sins' existence perpetuates the conflict between the goddess and demon races. Her plan is to wipe out both sides to prevent any future challenges to divine authority.

Meliodas discovers through his shared memories with the Demon King that the gods were created specifically to fight each other, meaning the Holy War was never a moral conflict but merely a game played by the divine beings. Using this knowledge, Meliodas and Zeldris combine their powers to overpower the Supreme Deity, though she warns that her death will unleash chaos upon the world.

Dahlia is a fairy and Dubs is the Giant Master Craftsman. Together, they have taken control of the Demon World and created enchanted weapons that allow them to mind-control fairies and giants. Their goal is to punish the Sins and their allies for defeating the Demon King, whom they served. They operate under the belief that the Demon King's defeat was unjust.

Zeldris helps free Meliodas and Elizabeth because despite their complicated history and divided duties, they remain brothers. Zeldris recognizes that Dahlia and Dubs are the true enemies and that Meliodas is needed to help defeat them. Their alliance is renewed through this rescue effort, setting up their eventual cooperation against the Supreme Deity.

Earlier on the road, Meliodas and Zeldris compare notes about their duties and vows, showing their underlying familial bond.

The Goddess Race is revived and attacks on the orders of the Supreme Deity herself. After the Sins defeated the Demon King, the Supreme Deity decides to eliminate the Sins and destroy both races involved in the Holy War. Mael arrives to warn Liones of this imminent attack, which represents the Supreme Deity's final attempt to control the outcome of the long-standing conflict.

Merlin tells Arthur that with the Supreme Deity's demise, the Age of Humans and Chaos can truly begin. This refers to a new era where humans are no longer controlled or influenced by the warring god factions, the Demon King and Supreme Deity. Arthur's role as king becomes central to this new age, as the balance of power shifts away from the divine beings who have manipulated mortal affairs.

Escanor, the Lion Sin of Pride, is absent because he sacrificed his life during the final battle against the Demon King in the main series. His death marked the great cost of victory mentioned in the movie's description. The Sins disbanded after this loss, and the movie takes place six months later with each Sin pursuing their own journey.

The movie's opening establishes that peace came at a great cost, specifically referencing Escanor's sacrifice.

The attacks are coordinated by Dahlia and Dubs as part of their revenge plan against the Sins. They use enchanted weapons to control fairies and giants, sending them to attack both locations at once, the Fairy King's Forest where King and Diane are marrying, and Liones where Bartra's coronation is taking place. This strategic timing is meant to overwhelm the Sins and their allies.

The timeline shows both events occurring during the same period, and earlier the demon warned of the fairy-giant takeover in the Demon World.

The enchanted weapons crafted by Dubs maintain Dahlia's enchantment over the controlled fairies and giants. The Sins defeat the attacks by disarming these weapons, which breaks the enchantment and frees the mind-controlled forces. This reveals the core weakness of Dahlia and Dubs's plan, the enchantment depends entirely on the physical weapons.