Fjosok is a supporting character in the anime Ronja the Robber's Daughter. He is a member of Mattis's band of robbers and holds a position of significant responsibility within the group, acting as Mattis's trusted right-hand man. In the band's hierarchy, he is described as being next in seniority after the elder robber Skalle-Per.

In terms of background, Fjosok is shown to be present from the very beginning of the story, as he is among the robbers gathered at Mattis's fort on the night Ronja is born, inquiring about her name. His physical appearance includes brown eyes, black hair worn at shoulder length, and he is often seen with a mustache and a bandana.

Personality-wise, Fjosok is characterized by a calm and composed demeanor. He is consistently loyal to Mattis, the chief of the band, and offers his support in various situations without voicing open criticism. This loyalty, however, is not without its limits, as Lovis, Mattis's wife, once scolds Fjosok for failing to fulfill his duties while he is busy supporting the chief. He is also shown to be approachable and willing to engage with Ronja on topics her father avoids, such as discussing what it truly means to be a robber.

Fjosok's primary motivation within the story stems from his loyalty to the clan and his position as Mattis's right-hand man. His role is to support the chief and the band, maintaining order and offering counsel. He serves as a dependable presence among the robbers, contributing to the daily life and operations within Mattis's fort.

His key relationships are defined by this loyalty. He is a trusted subordinate to Mattis and a supportive, if occasionally scolded, comrade to Lovis. He interacts with Ronja with a degree of friendliness and openness, providing her with insights into the life of a robber that her own father is reluctant to share. While not related by blood, he functions as an extension of her family and community within the band.

Throughout the story, Fjosok remains a stable and consistent character. He does not undergo a major personal transformation but rather serves as a steady, anchoring presence for both the band's leader and for Ronja as she grows up. His development is shown through his continued reliability and his ongoing role as a bridge between Ronja and the adult world of the robbers.

Regarding notable abilities, Fjosok does not possess any magical or supernatural powers. His expertise lies in the practical skills expected of a seasoned robber in Mattis's band. His abilities include competence in navigating the dangerous forest and fulfilling the duties required of him as the chief's right-hand man.