Eugen is a 50-year-old human mercenary with dark brown hair and eyes, standing 174 cm tall. He possesses significant combat experience and physical strength, with hobbies including weightlifting and fishing. He enjoys sweets but actively avoids interactions with children.

Originally a skyfarer traveling alongside Rackam, Eugen later returned to his homeland in the Auguste Isles. There, he worked as a mercenary opposing the Erste Empire's expansion. His past includes a significant connection to the Black Knight, though he consistently attempts to distance himself from this history, citing his age as a reason to avoid further entanglement. This pattern of evasion defines much of his early character.

His encounter with the main crew occurs during an attempt to flee his obligations. Despite initial reluctance, he chooses to join their journey, recognizing the need to confront his past. This decision marks a shift from avoidance to active participation, particularly in standing against the Empire and addressing unresolved matters tied to the Black Knight.

Eugen often presents a gruff and pragmatic exterior, yet he provides tactical wisdom during conflicts, drawing on years of accumulated experience. His sayings and insights sometimes puzzle others but reflect a deeper understanding. As part of the crew, he serves as a seasoned combatant and strategist, contributing to battles against primal beasts and imperial forces.

While his background with the Black Knight remains largely undefined, it represents a core aspect of his character development. His journey with the crew facilitates gradual acceptance of his responsibilities, moving away from his earlier tendency to retreat from challenges.