Furina

To understand Neuvillette at a cosmic and biological level, one must trace the history of Teyvat back to the Old World before the arrival of the Primordial One (the Heavenly Principles). In that primordial era, the Seven Sovereigns—supreme elemental dragons—ruled the planet, with the original Hydro Dragon Sovereign serving as the living heart of the Primordial Sea itself. After the Heavenly Principles vanquished the Sovereigns and usurped a major portion of their elemental Authorities to forge the seven divine thrones of the Archons, a prophecy foretold that the successor to the Hydro Dragon would eventually be born in human form after the original Hydro Dragon's remains had prevented the Enkanomiyan Bathysmal Vishaps from evolving into a pure vessel.

Because Neuvillette incarnated directly into a mortal-shaped body, he lacks a portion of his predecessor's pre-reincarnation memories and spent centuries struggling to comprehend why he existed in human skin. Physically, his draconic biology manifests in his vertical slit pupils with pale-violet irises, his pointed ears, and the twin luminous blue-and-indigo horn-like feelers (antennae) flowing down through his long silver-white hair, which glow radiantly with Pneuma energy whenever he invokes his full Sovereign power. Unlike Archons who rely on Gnoses or mortals who require Visions, Neuvillette's constellation is simply 'Leviathan'—his own self—and following Focalors's execution, he possesses the complete, unbridled Authority of the Hydro Dragon Sovereign.

Following his reincarnation into human form several centuries ago, Neuvillette lived in quiet confusion away from human civilization until he received an anonymous invitation letter—written by the Hydro Archon Focalors—encouraging him to take a seat at the Opera Epiclese in the Court of Fontaine and serve as the nation's Chief Justice. Hoping that observing human trials, passions, and tragedies would help him answer the existential question of why he had been born in a human body, Neuvillette accepted the post of Iudex alongside the public persona of 'Furina.'

Roughly four hundred years before the Traveler's arrival, Neuvillette made one of his most enduring civic decisions: welcoming the Melusines—diminutive, gentle creatures born from the flesh and blood tokens inside the corpse of the Abyssal dragon Elynas—into the Court of Fontaine. Recognizing the Melusines' innate kindness and unique visual perception despite rampant human prejudice at the time, Neuvillette established the Marechaussee Phantom investigative agency for them and enacted strict laws declaring that Melusines must be addressed with the respectful pronoun 'she/her' rather than 'it.'

Wait—even that reform came at a painful cost when a Melusine officer named Carole sacrificed her life to stop a staged political riot orchestrated by conservative conspirators who resented Neuvillette's reforms, while the honorable Captain Vautrin took vengeance in court to prove his loyalty to the Iudex. Through four centuries of presiding over trials alongside the Oratrice Mecanique d'Analyse Cardinale, Neuvillette gradually came to love humanity and the people of Fontaine far more deeply than he himself realized.