Magno Vivian is the elderly commander of the pirate vessel Nirvana, where she is universally referred to as Boss by her crew. She is a first-generation colonist from Earth, having originally been onboard the colony ship Ikazuchi during humanity's initial expansion into the galaxy. By the time of the series, she is over one hundred years old, and her advanced age marks her as a living repository of knowledge and wisdom. Her perspective is unique, as she carries memories from a time before the human race divided into the separate male and female societies of Tarak and Mejere. This background gives her a broad understanding of both genders, and she often dispenses advice and directs the crew's duties with this inclusive wisdom in mind.

In terms of personality, Magno is a calm and commanding presence, rarely seen without a placid, knowing smile. She serves as the steady, guiding hand for the more impulsive members of her crew. Despite her age and frail appearance, she possesses a sharp intellect and a keen understanding of the people under her charge. Her personality leans towards a maternal or grandmotherly archetype, offering support and a listening ear. For instance, she develops a particularly strong, mother-like bond with the young pilot Bart Garsus, providing him with guidance and comfort. She also has a habit of calling the protagonist Hibiki Tokai little one rather than using his name.

Magno's primary role is the strategic leader of the Nirvana. She holds the ultimate authority on the ship and is responsible for making critical decisions regarding navigation, combat, and the overall mission. Her motivations are rooted in her ancient history as a colonist; she seeks to navigate the dangerous present while holding onto the knowledge of a unified human past. The mystery of her past connects directly to Hibiki, as she possesses a photograph of herself on the Ikazuchi holding him as an infant. While this has led to speculation that she may be his sister, it is more strongly suggested that she was simply a young friend of the family who often visited him. This connection gives her a vested, almost protective interest in Hibiki's development and the unity between the men and women on her ship.

Throughout the second stage, Magno's role remains that of the anchor for the Nirvana. She offers strategic counsel and emotional support as the crew faces new, more powerful enemies. Her key relationships include those with her second-in-command, Buzam A. Calessa (B.C.), and the hot-headed Gascogne, who act as her primary enforcers and trusted subordinates. Her relationship with Bart deepens, further cementing her role as a stabilizing, parental figure on a ship filled with young soldiers.

While she does not pilot a Dread or engage in direct combat, her notable ability lies in her strategic mind and her extensive historical knowledge. She maintains order among a disparate group of male and female pirates who have been enemies for generations. Additionally, it is implied that she suffers from a secret heart condition, as she is occasionally seen clutching her chest in pain, a weakness she keeps hidden from the rest of the crew. This hidden ailment underscores her determination to project strength and stability for as long as her crew needs her. Her development is subtle, defined not by a change in her own personality but by the gradual revelation of her past and the eventual acceptance that the future of humanity lies with the younger generation she commands.