Moonlight Treasure King Gu

Gu Yue Bo tells Fang Zheng that the clan’s deepest research on Moonlight Gu includes two rank five recipes. Fang Zheng already holds Jade Skin Gu and Moonlight Gu, which satisfies one of those recipes. Following it through multiple fusions would eventually yield rank five Moonlight Treasure King Gu. Bo then sets that rank five result aside as too early to dwell on, and teaches the rank two first step, Moon Raiment, instead. ^{ch. 98}

Rank

Fang Zheng’s Moonlight Gu and Jade Skin Gu route has an upper limit of rank five, becoming Moonlight Treasure King Gu. ^{ch. 106}

Recipe line

Fang Yuan later lists that fusion among several Moonlight Gu advancement paths, and calls Fang Zheng’s route a rare one. He also states that holding a rank five recipe does not mean a rank five Gu can actually be made. Fusion success rate falls as rank rises, and many rank five Gu Masters still have no rank five Gu. ^{ch. 106}

Cited chapters never show anyone completing Moonlight Treasure King Gu or using a finished copy.