From the PDF introduction:
The Legend of the White Snake is an elaborate story derived from an ancient Chinese legend that originated in Hangzhou, China, which was told perhaps as early as the Tang Dynasty (circa 600 A.D.). The story continued to develop through oral tradition and was eventually recorded during the Ming Dynasty (circa 1300 A.D.). Although the story has developed and changed over time, the central story has not. It features a green turtle and a white snake who become human and the turtle-man falls in love with the beautiful white snake-woman. The woman, however, is offered an umbrella by a human and she falls in love with him and they soon marry. The turtle man, seeking revenge for his unrequited love, becomes a great cleric so he can turn the woman back into a white snake before her husband’s very eyes. The man and the turtle fight a great battle, and although the man wins, the evil cleric casts a spell that separates the couple forever.
From the Cover:
Originating in Hangzhou, China, this ancient legend tells of a turtle and white snake who become human immortals. The turtle-man falls in love with the white snake-woman, but she rebukes him for a human whom she marries. The turtle, in anger, seeks his revenge by becoming a great cleric, turning the woman back to a white snake before her husband’s very eyes and separating the two forever. Can the adventuring party survive the island of the mist dragons and reunite the white snake with her husband Xu Xian? Find out in this famous Chinese legend – The Legend of the White Snake – now, for the first time, a First Edition Advanced Dungeons & Dragons adventure!