Ferdinand, son of Ehrenfest's sixth Archduke and Seradina, a princess of Lanzenave, was born under the name "Quinta" in the Sovereignty. He grew up in a villa assessing children's mana levels; those not chosen as Lanzenave's next king faced execution. Ferdinand escaped execution and fled to Ehrenfest, where the Archduke adopted him, renaming him. His mother was executed in his place. In Ehrenfest, his stepmother Veronica persecuted him, poisoning his food and assigning untrustworthy retainers. This abuse fostered a deep distrust of women and immunity to poisons.

Initially living outside the castle due to Veronica, Ferdinand moved inside after his baptism. He formed bonds with his half-brother Sylvester and cousin Karstedt, resisting Sylvester's early friendship attempts. Ferdinand excelled at the Royal Academy, graduating top of his class in scholar, knight, and archduke candidate courses. His strategic skill in ditter won him a distinctive blue cape from a Dunkelfelger knight, which he wore after relinquishing his Ehrenfest ocher cape upon joining the temple. His Academy achievements included partially completing Zent candidate trials and obtaining a third of the Book of Mestionora.

Escalating threats from Veronica led Ferdinand to join the Ehrenfest temple at Sylvester's suggestion, forfeiting his noble status. As High Priest, he managed temple operations and rituals, initially bored until Sylvester delegated administrative work. Mana shortages during the Sovereignty's civil war increased his duties, causing overwork and reliance on rejuvenation potions. His strict security included avoiding temple meals due to poisoning risks.

Ferdinand became guardian and mentor to Myne after she entered the temple as a blue shrine maiden apprentice. Recognizing her high mana and value to Ehrenfest, he educated her in noble etiquette, magic, and temple duties. Their relationship was initially formal; he criticized her impulsiveness but acknowledged her intelligence and work ethic. Key events included sentencing her to the repentance chamber for withholding trombe information and mediating conflicts involving her friend Lutz's family. When knights' negligence led to her injury during trombe extermination, Ferdinand used a memory-viewing tool, discovering her past life as Urano Motosu. This shared experience deepened their bond, leading him to arrange her adoption into the Karstedt family for protection.

Ferdinand's role expanded as Myne became Rozemyne. He supported her orphanage reforms and printing initiatives while managing political threats. His strategy was evident in purging Veronica's faction and positioning Ehrenfest favorably. Forced into a political marriage with Ahrensbach by royal decree, he maintained ties to Rozemyne, eventually becoming engaged to her to preserve their familial connection under Alexandria's new archducal structure, fulfilling his desire for genuine family bonds.

Later events revealed Ferdinand's royal lineage and Zent eligibility. During the country's foundation crisis, he demonstrated decisive leadership, neutralizing rival candidate Gervasio and negotiating the royal family's surrender. His solution revived ancient rituals for selecting future Zents without bloodshed, aligning with the gods' wishes. He declined the Zent position, instead supporting Rozemyne as Aub Alexandria while serving as her High Priest and fiancé.

Personality-wise, Ferdinand is reserved and pragmatic, highly disciplined with a strong focus on efficiency and competence. He seldom expresses emotions openly, often masking discomfort with a smile. His harsh upbringing fostered cynicism and impatience, especially toward incompetence. Despite this, he shows deep loyalty to trusted individuals like Sylvester and Rozemyne, expressing care indirectly through actions like creating protective magic tools. He values research and intellectual pursuits, sometimes neglecting basic needs during study. His complex character blends ruthless pragmatism in conflict with underlying vulnerability from his lifelong yearning for familial acceptance.