"Berserk: The Golden Age Arc III - The Advent" is the third and final installment in the Golden Age Arc film trilogy, adapting the latter portion of the Golden Age arc from Kentaro Miura's manga "Berserk." The story continues the tragic and intense narrative of Guts, Griffith, and the Band of the Hawk, focusing on the culmination of their struggles and the devastating consequences of their choices.

Following the rescue of Griffith from the dungeons of Midland, the Band of the Hawk faces dire circumstances. Griffith, once a charismatic and ambitious leader, is left physically broken and emotionally shattered after enduring prolonged torture. His inability to lead or fight plunges the group into disarray, leaving Guts and Casca to shoulder the burden of maintaining morale and direction. Guts, grappling with his own sense of purpose, decides to leave the Band of the Hawk to pursue his own path, a decision that deeply affects Griffith and Casca.

Griffith's despair reaches a critical point, leading him to activate the Crimson Behelit, a mysterious artifact tied to otherworldly forces. This act triggers the Eclipse, a catastrophic event where the God Hand, a group of demonic entities, offers Griffith a choice: sacrifice his comrades to ascend as one of them. In a moment of desperation, Griffith accepts, betraying the Band of the Hawk and unleashing a nightmarish onslaught. The Apostles, monstrous beings serving the God Hand, massacre the group, leaving Guts and Casca as the sole survivors. Guts, driven by rage and grief, confronts Griffith but is unable to prevent the transformation of his former friend into Femto, a member of the God Hand.

The film concludes with Guts and Casca escaping the Eclipse, though not without profound physical and emotional scars. Casca is left traumatized and mentally broken, while Guts resolves to seek vengeance against Griffith and the forces that orchestrated the tragedy. The Advent sets the stage for the darker, more supernatural direction of the overarching "Berserk" narrative, marking a pivotal turning point in the lives of its central characters. The story explores themes of ambition, betrayal, and the cost of power, delivering a harrowing and unforgettable conclusion to the Golden Age Arc.