"Wild Arms: Twilight Venom" is a 22-episode anime series that aired in 1999, based on the "Wild Arms" video game franchise. The story is set in the fictional world of Filgaia, a desolate, desert-like planet where humanity struggles to survive amidst dwindling resources and the remnants of ancient technology. The narrative centers on a group of characters brought together by fate to confront a looming threat to their world.

The protagonist, Sheyenne Rainstorm, is a drifter with a mysterious past and a unique ability to wield the ARMs, ancient weapons of immense power. Sheyenne is joined by Kiel Aronax, a young and idealistic scholar seeking to uncover the secrets of Filgaia's lost civilizations, and Loretta Oratorio, a skilled fighter and bounty hunter with a tragic personal history. Together, they form an unlikely alliance to combat the forces of darkness threatening their world.

The primary antagonist is the organization known as Odessa, led by the enigmatic Lord Blazer. Odessa seeks to harness the power of the ARMs and the ancient technology of Filgaia to dominate the world. As the series progresses, it becomes clear that Odessa's goals are tied to the resurgence of an ancient evil, the Venom, a destructive force that once nearly annihilated Filgaia. The Venom's return is facilitated by the misuse of ARMs and the exploitation of Filgaia's fragile ecosystem.

Throughout the series, the characters embark on a journey across Filgaia, encountering various factions, allies, and enemies. They uncover the truth about the ARMs, the history of Filgaia, and the role of the Venom in the planet's decline. The narrative explores themes of environmental degradation, the consequences of technological misuse, and the resilience of humanity in the face of existential threats.

Key supporting characters include Isaac, a former soldier with a deep sense of duty, and Mirabelle, a mysterious woman with ties to the ARMs and the Venom. Their interactions and backstories add depth to the overarching plot, revealing connections between the characters and the larger conflict.

The series builds toward a climactic confrontation between Sheyenne and his companions and the forces of Odessa, culminating in a battle to prevent the Venom from consuming Filgaia. The resolution ties together the personal struggles of the characters with the fate of their world, emphasizing themes of sacrifice, redemption, and hope for the future.