Nonna Zell is a young Immanity girl who lived during the Great War, the cataclysmic conflict that ravaged the world six thousand years before the events of the main series. She is the daughter of Ivan Zell and is entrusted to the care of Riku Dola after her father's death, making her a member of the last surviving human colony led by Riku. Her appearance is characterized by short black hair and fair skin, and she shares several physical similarities with her distant descendant, Chlammy Zell.

In the story of No Game No Life Zero, Nonna Zell serves as a supporting character representing the fragile hope and continuation of humanity during the war. Her motivation is simply to survive alongside the other Imanity in the colony. She does not possess any magical abilities or combat skills, as Immanity are the only race unable to use magic. Instead, she depends on the protection and leadership of Riku and the other adults. Her role is primarily symbolic: she embodies the future that Riku and Shuvi fight to protect, and her survival after the war ensures the lineage that eventually leads to Chlammy Zell in the present day.

Personality-wise, Nonna Zell is portrayed as a quiet, cautious child, aware of the dangers surrounding her. She is loyal to those who care for her and, despite her young age, shows resilience in the face of constant threat. Her key relationship is with Riku, whom she trusts as a guardian figure after her father's death. She also interacts with other members of the colony, including Corounne Dola. Over the course of the film, Nonna does not undergo significant character development; rather, she remains a constant reminder of the innocent lives caught in the war. Her notable ability is not supernatural but lies in her endurance and the hope she represents as a survivor who carries the legacy of her people into the next era.