Felix Argyle (フェリックス・アーガイル), commonly known as Ferris (フェリス), is Crusch Karsten's knight.
Ferris has flax colored hair and yellow eyes. His casual wear consists of a blue collar with a ribbon, a blue dress, black tights, blue leggings, blue shoes, white arm covers, and a blue scarf tied around his right arm.
Ferris' cat like appendages are a result of his ancestors having Demi Human blood and because of this, he was mistreated by his parents. The white and blue ribbons that he wears in his hair are a gift from Crusch and he always wears them no matter what he's wearing.
Ferris usually refers to himself in third person, calling himself Ferri-chan (フェリちゃん), though he will refer to himself as Ferris, Felix, or with female pronouns depending on the situation. He is absolutely loyal to Crusch and will do anything she says, however he will oppose her if needed. He also enjoys teasing other people, especially those that are surprised that he's male, using cutesy language and gestures to agitate them.
Although he hides it through his actions and words, Ferris has a severe view on death and values due to his job as a healer, leading him to hold those who no longer have any will to live in contempt from the bottom of his heart. He also hates weaklings because of his complex, causing him to hate Subaru for a while, however he lets go of his feelings against him after seeing his actions during the battle against the Hakugei.
Ferris can get emotional when it comes to Crusch, such as the time when she was infected by Capella's dragon blood, becoming visibly stressed by her poor condition and even going as far as to demand to see a captured Sirius so he could torture her to gain information on how to cure her. He is constantly thankful for Crusch and everything that she's done for him in her life.
From the moment Ferris was born, he had cat like appendages due to his ancestors having Demi Human blood, causing his parents to mistreat him as they suspected an affair. He was locked in the basement of the Argyle Mansion for the first nine years of his life and was barely cared for. When Crusch found him, she described him as "a fragile boy who was painfully thin, was black from being covered in dirt and filth, and couldn't talk properly". He was subsequently taken to the Karsten Mansion to be cared for and made Crusch attendant while his parents lost what little standing they had with the Karsten family, leading to their decline.
In the following years to come Ferris would establish a strong sense of loyalty and devotion towards Crusch for taking him form the hell that was his life before and base part of his new identity on that relationship. He also came to befriend Fourier Lugnica a little while after the prince met Crusch. Together 3 would get into all kinds of mischief that defined much of their friendship.
At age 18, Ferris would join the Royal Guard under recommendations from Fourier and Royal Institute of Healing. Although he wanted to be of better use to Crusch, Ferris at first was not very comfortable in being the elite group for several reasons, he stood out due to his odd features marking him as a demi-human, his preference for wearing women's clothing, his own lacking combat abilities and lastly dissatisfaction of his unusual and sudden appointment despite all that from the other knights. However, on the first day, he also came to be acquainted with Reinhard van Astrea and Julius Juukulius which would be the first step in breaking the wall between Ferris and his new environment. Through his good relationship with both of them and the subtle opportunities to display his worth crafty granted by Marcos Gildark, Ferris would come to earn the respect of the other knights for saving their lives with his magic. This would come to give him a sense of his abilities and place there.
In the last month of his probationary period in the Royal Guard before he became a permanent member, dark rumors surrounding his old family would reach his ears via Fourier. Learning that Crusch had gone to investigate them, Ferris together with Fourier and Julius would rush back to the Karsten estate to learn the truth of the situation. After their arrival, things would take a turn for worse when they learn that Crusch had been captured and her men were engaged an with an undead army outside the Argyle household. Ferris would also receive a message from his father that would demand he come to Argyle estate alone in exchange for saving Crusch. Returning to Argyle mansion for the first time in nearly a decade Ferris would confront his father and a maid named Hannah who he felt a familiar connection to. Following a cold reunion, Ferris would acquiesce to his father's demand to revive his mother with the Argyle's family ancient spell. However, when Ferris was brought to the master bedroom, and examined his mother's corpse he would come to the shocking conclusion that she was murdered due to the numerous and frenetic stab wounds in her body, partially thanks to Biehn's meticulous preservation. After a tense argument between Ferris and Biehn to which the later would lose his composure admit his guilt in the matter. Eventually realizing any further discussion was pointless Ferris revived the woman. The spell, however, ended up being a partial failure as despite his mother seemingly coming back with some part of her personality. Moreover, the now undead mother would kill Biehn as they embraced then crumbled into ash a moment. Hannah would then reveal to Ferris where Crusch was being held and that she had already free her from her bonds. Just as Ferris raced out of the room, he would hear the locking and smoke coming from the room. Despite his protest, Hannah would not open the door choosing to die along with her master and mistress. The event marked a scar on Ferris' heart and where he developed deep hate for those who easily gave up their lives. He would meet Crusch and Julius in the foyer of the manor, relieve but utterly distraught by the whole event and escape the burning building with them.
After the incident, Fourier would collapse from a mysterious illness and Ferris would spend a year looking after him. Desperate and frustrated at the lack of progress Ferris would consider using the "Immortal King's Sacrament" to revive him after death but Fourier would forbid it and wanting to be allowed to die on his own terms if that was the case. They share a somber heart to heart moment and Fourier would pass away a couple of days later. On that same day, Ferris would take his oath of knighthood to Crusch to support her and Fourier's memory.
Divine Protection (加護 Kago): Ferris has the Divine Protection of Water (水の加護 Mizu no Kago), which makes him highly skilled at Water Magic.
Magic User: Ferris has extraordinary power and talent with water magic thanks to the combination of his bloodline and Divine Protection.
- Healing Magic: Ferris is considered to be the best Water Magic user on the continent, earning him the alias of Blue (青 Ao). He is also the youngest to be given this alias. By directing mana to anyone whose Od he's interfered with, he can make their body go out of control, enabling him to do things such as using their body like a puppet or destroying the circulatory system of their gates from inside. He can also die and heal himself to perfect condition, as shown during the battle against Petelguese, however it is unknown how many times he can do this.
- Immortal King's Sacrament (不死王の秘蹟 Fushiou no Hiseki): Ferris learned this magic from Biehn Argyle. The "Immortal King's Sacrament" is a spell used to resurrect people from the dead, though the effect of the magic depends on the skill of the user and how much they understand about the magic otherwise they will only be able to resurrect people as zombies. The spell had originally been invented by a witch who said to be able bring back a person just they were in life, but that part of the spell had been lost.
Pseudo-Immortality: One way Ferris body differs from most humans and demi-humans is his extraordinary connection with Water Mana imbue it with strong passive effect in which results in rapid cellular regeneration. With this in effect, it means he can recover from any fatal wound that doesn't kill him outright. However, in exchange it further weakens his ability to fight.
Equipment: Ferris owns a short sword he received from Crusch, but as he doesn't like to damage his skin, he generally refuses to wield it. He has wielded it once in an effort to intimidate an unimpressed Capella.
- According to the author, Ferris' birthday is January 16.