Xu Xian originates from Chinese mythology as a human character central to the Legend of the White Snake, one of China's four great folk tales. He is depicted as a scholar or physician residing in Lin'an Prefecture (modern Hangzhou) during the Song Dynasty. His early life involves an encounter with the immortal Lü Dongbin, who sells him tangyuan (sweet dumplings) that are actually immortality pills. After consuming them, Xu Xian vomits the pills into West Lake, where they are consumed by a white snake spirit (Bai Suzhen), granting her 500 years of magical power and establishing a fated connection between them. During the Qingming Festival, Xu Xian meets Bai Suzhen and her companion Xiaoqing at the Broken Bridge by West Lake. He lends them his umbrella during rain, leading to their courtship and marriage. Their relationship forms the core of the narrative, complicated by Bai Suzhen's true identity as a snake spirit. Xu Xian's discovery of her nature varies: in some versions, he dies of shock upon seeing her transformed form after she drinks realgar wine; in others, he initially rejects her but later reconciles. Bai Suzhen often revives him using magical herbs stolen from Mount Emei. Xu Xian's character development hinges on his conflicted loyalty between Bai Suzhen and the Buddhist monk Fahai, who seeks to suppress her. In traditional versions like Feng Menglong's *Stories to Caution the World*, Xu Xian (called Xu Xuan) is portrayed as easily manipulated by Fahai, contributing to Bai Suzhen's imprisonment. Later adaptations, such as the 18th-century opera *The Legend of Leifeng Tower*, show him betraying Bai Suzhen to Fahai after the birth of their son, Xu Shilin, and subsequently becoming a monk. Conversely, modern interpretations like the 1992 TV series *The New Legend of Lady White* emphasize Xu Xian's unwavering love, where he accepts Bai Suzhen's true identity and remains loyal. In the 2019 animated film *White Snake*, Xu Xian appears as "Ah Xuan," a snake hunter from a village capturing snakes for the antagonistic General. This iteration diverges by depicting him as a chivalrous figure ("youxia") who prioritizes moral integrity over societal prejudices. After discovering Blanca's (Bai Suzhen) identity as a snake spirit, he chooses to become a low-level demon to bridge their species divide, sacrificing his humanity. His knowledge of medicine and Taoist occultism proves instrumental in confronting adversaries, though his demonic transformation renders him permanently vulnerable. The film establishes a past-life connection where Xu Xian rescues Bai Suzhen in a previous incarnation, motivating her centuries-long search for his reincarnation. Xu Xian's legacy extends through his son, Xu Shilin, born after Bai Suzhen's imprisonment in Leifeng Pagoda. In some versions, Xu Shilin becomes a top scholar (Zhuangyuan) and secures Bai Suzhen's release through imperial intervention or filial devotion, contrasting with Xu Xian's inability to save her. Xu Xian's character arc concludes with him aging as a monk or dying before Bai Suzhen's liberation.