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 Sacrament of the Immortal King", 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 any slaves being 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 (魔法使い Maho Tsukai): Biehn was a highly talented user of Water Magic.
- 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.
- Sacrament of the Immortal King (不死王の秘蹟 Fushiou no Hiseki): The Sacrament of the Immortal King is an ancient and incredibly powerful spell, created by an unknown Witch ages ago. The spell, when cast correctly, will allow the user to reanimate corpses of the dead and make them do their bidding. Sadly, the technique to properly cast the spell has been long lost to time, and only an incomplete incantation exists which was transcribed in an old and withered book regarded as the most important heirloom of House Argyle. Originally, however, the spell was thought to be capable of fully reviving a dead person, and there are legends of the aforementioned Witch being supposedly capable of bringing back people exactly as they were before their demise. Sadly, though, that part of the spell has not been transcribed and has been long lost to history, with no hope of ever regaining it. Effectively, the written chunks of the spell's full passage is incapable of producing anything more than walking corpses with no will of their own, whose flesh slowly withers away and decomposes through time. To further limit the usefulness of this mostly-lost spell, a caster with natural affinity for the spell must be found in order to recreate even the most basic effects of this forbidden magic – an affinity so rare, that no known person had possessed it in over a century. Finally, it should be worth bringing up that once successfully reanimating a dead person, their soul will not return to the body and they'll be nothing more than a clump of decomposing flesh. Even after persistent refinement, Biehn could only create zombies. There didn't appear to be a limit to the amount of zombies he could create and command, as he had no issue reviving over two-hundred people simultaneously.
- 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 an altercation is not known.
- "It was one of the exceptional magics, supposedly created by a witch who held the world in thrall, before the knowledge was lost." Re:Zero Ex Light Novel Volume 1 Felix Argyle's Curse; Section 8
- "Put briefly, it allowed the user to control corpses according to their will." Re:Zero Ex Light Novel Volume 1 Felix Argyle's Curse; Section 8
- "Look at this! This is the text describing the Sacrament of the Immortal King, that has been passed down in our house. Biehn dug in his bag and pulled out a worn book." Re:Zero Ex Light Novel Volume 1 Felix Argyle's Curse; Section 11
- "The Witch who invented the spell had been said to be able to bring the dead back, looking exactly as they had in life..." Re:Zero Ex Light Novel Volume 1 Felix Argyle's Curse; Section 8
- "...but that part of the spell had not been passed down." Re:Zero Ex Light Novel Volume 1 Felix Argyle's Curse; Section 8
- "It's not just that the spell book is incomplete. It was never a question of the power as a spell caster. Using an awful spell like that – forcing a body that's stopped to start again – of course it was going to break down right away." Re:Zero Ex Light Novel Volume 1 Felix Argyle's Curse; Section 11
- "And even the most basic manifestation was all but impossible to achieve without a caster who had a natural affinity for the spell. It was a very rare affinity – no one had been known to possess it in over a hundred years." Re:Zero Ex Light Novel Volume 1 Felix Argyle's Curse; Section 8
- "Though the flesh is revived, the soul does not reside within it. Reconstructing the Sacrament of the Immortal King is indeed difficult." Re:Zero Ex Light Novel Volume 2 The Love Song of the Sword Devil Fifth Stanza; Section 3