Yang Xi served in the fourth century CE as a medium employed by Xu Mi, an official of the Eastern Jin court, and Xu Mi's son Xu Hui, an aristocratic family with a serious existing interest in Daoist practice and the pursuit of transcendence. Beginning in 364 CE and continuing for roughly six years, Yang Xi reported receiving nocturnal visitations from a company of Perfected Immortals, zhenren, spiritual beings understood to occupy a rank above the ordinary immortals of earlier Daoist belief, who dictated to him an extensive body of new scripture, cosmological teaching, and practical instruction in meditation and visualization technique aimed at attaining their own exalted rank.
Yang Xi transcribed these revelations in his own hand, described by later tradition as calligraphy of unusual beauty that itself carried some of the authority of the message, and the material he produced for the Xu family over those years vastly exceeded in scope and sophistication anything the existing Daoist textual tradition of talismans and communal ritual, centered on the Celestial Masters lineage, had offered. Yang Xi alone among the household was recognized by the visiting immortals as their approved channel, a claim to unique authority that gave the resulting texts their weight within the family and, eventually, far beyond it.