Ferdinand is a central figure in the third part of the story, serving as the former High Priest of the temple in the duchy of Ehrenfest. He is the illegitimate son of the sixth archduke of Ehrenfest, making him the half-brother of the current archduke, Sylvester. His mother was Seradina, a princess from the foreign country of Lanzenave, and he was born under the name Quinta in a facility within the Royal Academy's Sovereignty. After being slated for execution, he was rescued and brought to Ehrenfest by the archduke, to whom he gave his name in an act of fealty. Because the archduke's first wife refused to accept him, Ferdinand was raised in a separate villa and later joined the temple on the advice of his brother to escape escalating political persecution from his stepmother.

Ferdinand has a sharp mind and a calm, dignified demeanor that often makes him seem older than his actual age. He is highly reserved and rarely shows emotion on his face, a trait born from a harsh and distrustful upbringing where he was constantly harassed and even had his food poisoned by his stepmother. This history has made him particularly cold and impatient with women and deeply suspicious of others. Despite his austere and pragmatic nature, which leads the protagonist to nickname him a demon lord or a mad scientist, he is not without kindness. He is deeply loyal to the very few people he trusts, such as his brother Sylvester, and is known to show his concern in roundabout ways rather than through direct expression. A notorious workaholic, he often forgets to eat or sleep when engrossed in research or administrative duties, a habit that frequently leads him to rely on rejuvenation potions.

Ferdinand's primary motivation is to ensure the stability and prosperity of the duchy of Ehrenfest. He works tirelessly behind the scenes as a discrete reformist, managing the temple's affairs and handling many of his brother's requests from the castle. He has a strong sense of duty and values competence above all else, despising laziness and incompetence, and he is known for cutting off anyone who cannot meet his high standards. When he encounters the protagonist, he initially sees her as a useful asset due to her vast mana and unusual knowledge, but he eventually becomes her primary guardian, mentor, and protector, motivated by a genuine, if often gruffly expressed, care for her well-being.

In the story, Ferdinand serves as the protagonist's direct superior in the temple and later as her guardian when she is adopted into nobility. He is the one who educates her in the ways of nobles, including etiquette, magic, and the harspiel. He is a calculating strategist who often manipulates events from the shadows to achieve the best outcome for Ehrenfest and to protect his charge from both internal and external threats. His position as High Priest gives him formal authority, but his true power lies in his political connections as the archduke's brother and his formidable personal abilities.

Ferdinand's key relationships are few but significant. He shares a close bond with his half-brother Sylvester, the current archduke, who he serves loyally and who is one of the few people who can see past his cold exterior. He is also childhood friends with Karstedt, a powerful local noble. His relationship with the protagonist, Rozemyne, is the most transformative. Initially viewing her as a troublesome but worthwhile pupil, he evolves into a fiercely protective mentor and father figure, becoming far more expressive and human through their interactions. Over time, he forms a deep, possessive attachment to her, driven in part by his envy of the loving family she has.

Ferdinand's character undergoes significant development over the course of the story. He begins as a solitary, beleaguered bureaucrat who is bored and exhausted by his mundane temple duties. Through his role as a teacher and guardian, he becomes more emotionally engaged with the world, allowing himself to care for another person deeply. While he is always a pragmatic chessmaster, his actions become motivated less by cold efficiency and more by a desire to protect his newfound family, leading him to eventually escape his lonely existence and seek a future where he can have companionship.

Ferdinand possesses an extensive array of notable abilities. He is an exceptional scholar and a trained knight, having completed all but one of the career tracks at the Royal Academy and becoming the top student of his year multiple times. He has a vast mana capacity and possesses seven-colored mana, granting him an aptitude for all seven primary gods. Due to years of having his food tampered with, he has acquired a strong resistance to poison. He is a brilliant strategist and a ruthless combat pragmatist who is known to use any means necessary to win. He is also an accomplished musician, his beautiful singing voice and skill with the harspiel being renowned among noblewomen. Furthermore, he owns one of the largest personal libraries in the country and is a learned researcher, particularly in the field of magic tool creation.