Fahai serves as the abbot of Jinshan Temple and the primary antagonist in the tale of Bai Suzhen and Xu Xian. His background varies: some adaptations present him as a human monk devoted to enforcing cosmic order, while others depict him as a terrapin or tortoise spirit who transformed into human form. This transformation was driven by jealousy towards Bai Suzhen after she gained greater magical power, sparking his enduring enmity. His core motivation arises from a rigid interpretation of Buddhist principles, demanding strict separation between spirits and humans. He perceives Bai Suzhen's marriage to Xu Xian as a violation of natural and divine laws. To dismantle their union, he first reveals Bai Suzhen's true serpent nature to Xu Xian. Later, he manipulates Xu Xian into offering her realgar wine during the Dragon Boat Festival, forcing her transformation and causing Xu Xian's fatal shock. After Bai Suzhen resurrects Xu Xian with a stolen herb, Fahai imprisons Xu Xian within Jinshan Temple, claiming this protects the mortal. Confronted by Bai Suzhen and her companion Xiaoqing demanding Xu Xian's freedom, Fahai summons protective Buddhist deities and employs magical artifacts, including an enchanted vestment that elevates the temple mountain to counter Bai Suzhen's flooding attack. The ensuing battle causes significant collateral damage, flooding lands and claiming civilian lives, yet Fahai remains resolute. He ultimately subdues Bai Suzhen—often while she is weakened by pregnancy—and imprisons her beneath Leifeng Pagoda, vowing she will emerge only when the pagoda collapses or the lake dries. Fahai's character has evolved substantially across retellings. Early Ming-dynasty versions, like Feng Menglong's 1624 story, frame him as a heroic protector of humanity from a malevolent spirit. Later adaptations, particularly during the Qing dynasty and modern eras, progressively vilify him, aligning with growing audience empathy for Bai Suzhen as a symbol of love resisting oppressive authority. Twentieth-century interpretations, influenced by socialist and anti-traditionalist movements, cement his role as an inflexible zealot. Tian Han's 1950s revision culminates in Fahai's defeat, the pagoda's destruction, and his retreat into a crab's stomach—a detail reinforcing perceptions of his tyranny. Certain narratives include divine retribution for Fahai; heavenly forces may shatter his artifacts or liberate Bai Suzhen, highlighting compassion's triumph over dogmatism. His unwavering commitment to "heavenly law" (tianli) and societal order remains consistent, though modern audiences frequently interpret this commitment as hypocrisy masking cruelty.