Báilián is a mysterious traveler introduced in the third season of Thunderbolt Fantasy, who makes his appearance in the country of Wanyu. He is a man with a striking appearance, characterized by his white hair, dark skin, and white garments. He is a guest character, conceptualized from a prototype figure from a long-running puppet series, bringing with him a sense of familiarity for long-time viewers. His voice is provided by a well-known Japanese voice actor.

In terms of personality, Báilián presents himself as humble and unassuming, famously referring to himself with a modest term that translates to "an inferior one". He rejects grandiose titles, stating that the notion of him being a god or a sage is an exaggeration and insisting he is simply an ordinary human being. This humility, however, belies a profound wisdom and keen observational skill. He demonstrates a thoughtful and cautious nature, contemplating the weight of his own actions as a stranger in a foreign land and suggesting that a well-intentioned deed does not always lead to a positive outcome. His demeanor is calm and polite, carrying an air of effortless insight.

Báilián's motivations are rooted in a sense of responsibility to confront evil, particularly when he witnesses the suffering of the people of Wanyu at the hands of demonic forces. His role in the story is that of a catalyst and a fellow traveler to the wandering swordsman, Shāng Bùhuàn. Though his appearance is brief, he serves as a crucial confidant, offering perspective and validation to Shāng Bùhuàn regarding the difficult path both have chosen to walk. He is a mirror, reflecting the burdens and ideals of a heroic journey that transcends the boundaries of their respective worlds.

Key relationships are limited but significant. His primary interaction is with Shāng Bùhuàn, whom he meets by chance. Their conversation reveals a deep mutual respect, as they recognize in each other a kindred spirit dedicated to a challenging and perilous mission. Rather than seeking to join forces directly, Báilián encourages Shāng Bùhuàn to continue on his own path, affirming that they are both walking the same road, though separated by time and space. He does not form bonds with the wider cast, serving instead as a singular, enlightening encounter for the protagonist.

Regarding development, as a guest character with limited screen time, Báilián does not undergo a personal transformation. He arrives as a fully realized figure of wisdom and departs on his own journey, leaving his ultimate destination unknown. His role is to impart perspective and to solidify the themes of the series' central hero, rather than to experience a personal arc.

Notable abilities include his profound insight. He is able to glance at the Magical Index, a catalogue of dangerous swords, and immediately grasp the complex cause-and-effect relationships that bind it, a feat that astonishes those around him. He also carries a personal sword which, while described by him as an ordinary weapon, possesses the unique and devastating property of being overwhelmingly effective against beings from the demon realm. This combination of sharp intellect and specialized martial power marks him as an individual of immense capability, despite his modest self-assessment. He is also referred to as the father of holy swords, implying a legendary status as a creator or originator of divine weapons.