Biehn Argyle (ビーン・アーガイル) was the once head of House Argyle, Ferris' father.
Biehn had a beard, long hair, big eyebrows and wore a suit.
A cold, delusional and heartless man seemingly on the verge of insanity. Although he supposedly loved his wife, he had none for his son due to his dominant demi-human traits manifesting from birth.
Several years earlier before Ferris came to live with Karstens, the Argyle family lost everything when it was discovered that Biehn and his wife had locked up their son Felix due to the discovery of demi-human blood in his body and to also hide the fact that one of Argyle's ancestors was a demi-human. After that couple had supposedly laid down quietly and live what meager possessions they still had in their home.
Some years later Biehn's wife would die. Distraught Biehn desperately sought means to revive her. After using his magic to preserve what he could of her body, Biehn would then turn to the Argyle clan's secret art "The Immortal King's Sacrament", a spell capable of resurrecting the dead and experiment with it for that purpose. However the spell was incomplete due to the other half of the inscription being lost over the ages and Biehn's power as a Water User wasn't enough to make up for it leading to the creation of a mindless undead, at best. These factors would bar much of his progress for years.
Then one day he would meet Miles, a merchant who dealt in antiques and slave trade. Miles would assist him in experiments by providing slaves as material for some time, a fact that would soon catch the attention of Crusch Karsten. Crusch and a company of around 50 of her soldiers would go to investigate the matter unaware that this was in fact a trap to lure her and ultimately Ferris back to the estate. With Crusch captured, the snare would work as intended as Biehn would force Ferris to come to the house and meet with him alone. There he would reveal his full plot that brings about a darker truth that there weren't slaves brought here but actual corpses that Biehn was currently using as an army to fight the Karsten militia outside the compound. Using Crusch's life as a bargaining chip, Biehn would demand that Ferris use the Immortal King's Sacrament to revive his wife, believing that his superior talent could make it work. With no choice Ferris does as requested and Biehn's wife seemingly returns to the world of the living. Although still looking like a malnourished husk nevertheless, Biehn was overjoyed but that would soon turn to horror as Hannah would suddenly strangle him to death with a serene smile on her deathly face.
Magic User: Biehn was a highly talented Water Magic spell caster.
- Healing Magic: While not quite on Ferris' level, Biehn is shown to be highly skilled in healing magic to the point he could recover wounds instantly and unconsciously without effort.
- Immortal King's Sacrament (不死王の秘蹟 Fushiou no Hiseki): 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.
- It is heavily implied that he might have had an affair with his maid, the only servant still living with him. Whether that lead to him stabbing his wife after altercation is not known.