Belzebuth serves as the fiercely loyal right-hand and personal bodyguard to Claude Jean Ellmeyer, the Demon Lord. His role is defined by an unwavering commitment to protect his master, reacting with immediate aggression and zero tolerance toward any perceived disrespect or threat to Claude's safety and honor. Initially, he presents a rough and intimidating exterior, appearing easily provoked and somewhat dimwitted, which is a defensive mechanism stemming from his lack of exposure to the formal etiquette and complex social circles of the noble court. His court, being small, did not necessitate such graces, leaving him blunt and prone to using anger as a shield for his more vulnerable feelings.

The arrival of Aileen Lauren d'Autriche is the catalyst for significant development in Belzebuth. She takes it upon herself to instruct him in proper manners, social etiquette, and other courtly graces, a gesture he genuinely appreciates. Through these lessons, he reveals a more endearing and sincere nature, becoming notably sweet and loyal to Aileen, whom he comes to respect deeply alongside his master. His personality is a blend of fierce protectiveness and an earnest desire to please, which occasionally leads to unintentionally humorous incidents due to lapses in common sense, such as mishandling poison or accidentally starting fires. These moments make him an unconventional but reliable figure within Claude's inner circle.

His primary motivation is maintaining the stability and well-being of Claude and Aileen, both individually and as a couple. When Claude suffers from memory loss due to an injury, Belzebuth actively collaborates with other allies, such as Keith Eigrid, to devise plans aimed at restoring the broken engagement between Claude and Aileen. Throughout these political and personal challenges, his dedication to Claude remains steadfast, showcasing his role as more than just a warrior, but also a loyal and supportive companion navigating the complexities of human nobility and emotional dynamics. While his background origins are not specified, his actions consistently emphasize unwavering service and a journey of personal growth. His notable abilities are not extensively detailed, but his primary function as a bodyguard implies formidable combat prowess and protective capabilities.