Sky Well Gu

Fang Yuan tells Li Xian that if blue sky Gu is to be advanced to rank five, the best method is to fuse it with sky well Gu to form rank five blue sky well Gu. ^{ch. 353}

Source and Southern Border

Fang Yuan names it a natural Gu found only on Eastern Sea’s Tian Jing island, adds that advancing will be troublesome for Li Xian, and says that in Southern Border only Yi clan might have sky well Gu. Li Xian repeats the chain blue sky Gu, sky well Gu, blue sky well Gu, and Tian Jing island when he wonders how Fang Yuan knows those names so clearly. ^{ch. 353}