𓈈 : Rien 𓂃 ࣪˖ ִֶָ

Name: Rien Occupation: The Index Nursefather, The Oracle's Proxy of the Index Affiliations: The Index, The House of Spiders Relations: Ryōshū (Daughter), Sora (Apprentice), Unnamed Wife, Unnamed Child

Appearance: Rien is a tall man with pale skin, black hair with silver strands, and a right eye featuring a golden pupil. The left side of his face is concealed behind a porcelain mask, the base of the mask being white, with a golden trim, used to obscure visible burns. The mask features a large crack along it. He wears a black suit jacket with golden buttons and an Index symbol on its left shoulder, with two similarly gold chevrons beneath it. His dress pants and shoes carry the same color as the rest of his suit, with the soles of his shoes having golden trim. Beneath his suit jacket, he wears a plain white dress shirt and black tie. He wears white gloves on his hands. In combat, he wields a golden vial with a chain on it, which allows for a ferrofluid-like liquid to transform into various weapons based on his assigned Prescript. Prior to Ryōshū's departure from the House of Spiders, Rien's left eye was exposed and undamaged. When removed, the mask reveals a scarred part of his face that also has a damaged eye, only showing his pupil from within the wound.

Personality: Rien is a composed individual, acting with simplicity and speaking gently even while harming himself or others. Though he acts with grace, he carries a sinister air, tormenting people both physically and mentally. Due to his allegiance to the Index, he shows extreme devoutness to orders of the Prescripts, going as far as maiming himself to prove the completion of his orders. Among the Nursefathers, he was the one who most readily assumed the role of father towards Yoshihide, reading books to her, reminding her to take care of her wounds, and even expressing a form of discontent in hearing of Valencina's physical abuse of her. Since Yoshihide's youth, he tended to treat her as younger than her actual age, which would annoy the girl; even when meeting her again during the main story, Rien's behavior towards her appears unchanged, with him often referring to Ryōshū as his "darling daughter" despite Ryōshū's unwavering will to sever herself from the Nursefathers. Out of the Nursefathers, Rien is also the most dedicated towards his task of perfecting Ryōshū into the perfect wielder of Arayashiki, rejoicing upon seeing her enter the state of non-self, and describing her as the House of Spiders' masterpiece Despite his unflappable demeanor, Rien harbors mixed feelings regarding the Prescripts. As it is due to them that he could indulge in sufferings and the pleasures of the City, Rien is thankful for the chance they allow him to enact great violence onto others; however, he conceals a resentment towards them, having harbored a genuine attachment for his previous family, which he had allowed to die by following the order of the Prescripts.

Prior to Now: In the past, Rien, under an unknown original name, followed the orders of the Prescripts delivered to him and obtained the title of The Oracle's Proxy of the Index; he then rose to the hazard level of Star of the City. At some point, the Prescripts led him to changing his name, creating a family, and soon after losing this family, and standing by as his wife and daughter died. While he attempted to delay the Prescript, taking trips away from his assigned tasks or ignoring the Prescripts outright, he would always end up fulfilling the given tasks. Even despite the deaths of his family, Rien continued on, harboring his memories of the past every day, masked under an aura of nothingness and blind devotion to the Prescripts. At some point in the past, the Prescripts ordered Rien to model his appearance on a particular Fixer who was "lost" to the Library. Whether this was before or after the task of raising a family is left unclear.

Among the five Fingers, Rien was the Index's representative in the House of Spiders, for the process of raising Ryōshū into a "perfect blade". While many of the other Nursefathers were not in direct contact with their respective Syndicates or no longer held a position of relevance within them, Rien remained an active member of the Index all through his time at the House, being the one who received and enforced the Prescripts regarding how to handle all matters related to Ryōshū's upbringing.

In her youth, Ryōshū was trained by Rien in a variety of manners, most especially including a wide variety of weapons, such as the "Spiral". While the other Nursefathers showed distance to the project of raising Ryōshū, Rien showed a far more prominent position in a father's role, frequently doting on and caring for a young Ryōshū.

Within his time as a member of the House of Spiders, Rien established and began maintaining a basement he accessed primarily through a door connected through the Corridor, allowing him to quickly travel back and forth. Within this basement, he would kidnap and keep specific individuals who would be pushed to take on attributes sought after by Prescripts, allowing for easy fulfillment of his missions. When questioned about the upper floor of the building by Araya, he claimed to have no idea where it led. In Ryōshū's youth, one of the books Rien read to her depicted a school, spurring a desire for her to go. Callisto, believing this to be a beneficial idea, told Rien he would be sending her to a Ring subsidiary academy. Rien allowed it as the Prescript approved, but said it was inadvisable. At a point in the past, Rien met with Ryōshū after having undertaken a Prescript that involved him having to stab a target through his own arm 38 times. While he was in pain, he informed Ryōshū of the severity of burning in comparison to his self-inflicted stab wounds, reminding her how much more painful it is; Rien chose to tell her to never burn somebody as a means of killing, provided they get the chance to curse her with their dying breaths. Taking the Nursefather's words lightly, Ryōshū chose to simply agree. On Ryōshū's departure, she inflicted Rien with a vicious burn across his face, leading to him adopting the mask he is seen wearing. After Ryōshū's departure from the House of Spiders, Rien began teaching an apprentice, Sora, who experiences intense devotion to both her master and the Prescripts which guide her. While Rien shows himself affable towards the girl acting as his apprentice, he remains deeply interested in Ryōshū.

The House of Spiders is a subsidiary of the Five Fingers formed around prominent members of each of the Fingers who came together for the shared goal of raising their "Yoshihide" into the wielder of the Arayashiki Relic. The organization was formed around three decades before the events of Limbus Company[2] and was initially composed of five "Nursefathers" and their daughter. Each of them later picked up an "Apprentice" after Ryōshū left, one to two years before the Prologue. Growing up, Yoshihide was trained for combat by the Nursefathers, though Valencina had the most personal investment in her skills as a fighter. All of them spent a great amount of time with her and presented her with different parenting styles. Valencina taught her the Palermitan Style of swordsmanship through physical abuse and an emphasis on manners;[28] Rien demonstrated how to use various weapons including the Zenon Tortoise Spiral with a gentle yet distant approach;[29] Callisto taught her the principles of the art of the Ring with a focus on Corporism; Matthias treated Yoshihide like a pet to pamper and was largely detached from discipline or learning; Shiomi Yoru trained her in the swordplay she practiced.[30] Several high-ranking Finger members would also occasionally visit the House as temporary tutors, such as Lei Heng and Émile Benoît.

Once an adult, Yoshihide took a child, Araya, under her care. When she eventually made up her mind to sever herself and her daughter from the control of the House of Spiders, Yoshihide hid Araya away in a Time Vault in the House,[31] which used T Corp. technology to alter the passage of time.[32] She then cut her way through the Nursefathers, severing Shiomi Yoru's tongue, Valencina's eye, Matthias's right arm, Callisto's prized artwork,[33] and burning half of Rien's face before making her escape with the intent of coming back for Araya later. Though Yoshihide lost the memory for a while, she also stabbed Shiomi Yoru in the heart, killing her. The Pinky Nursefather was later replaced by Araya after she left the safe prematurely.

In Yoshihide's absence, each of the five Nursefathers took in an Apprentice in the interest of replacing Yoshihide as children and as tools.[3][34] The Thumb Apprentice Lucio was trained by Valencina specifically to be a "textbook" for Yoshihide to relearn her techniques from,[35] the Index Proxy Sora was trained by Rien, the Apprentice Kira was trained by Matthias, the apprentice Albina was trained by Callisto, and the apprentice Ren was trained by the Dihui Star to both fight and act as her mouthpiece.