Yin Yang Rotation Gu

Yin Gu used on a male body turns yang into yin and makes the target a woman. Yang Gu used on a female body turns yin into yang and makes the target a man. Fang Yuan calls Yin Gu a rank four healing Gu with the effect of bringing the dead to life, and states that using it lowers the Gu Master’s aptitude by ten percent. For a ten extreme physique, that drop is not permanent: as cultivation continues, aptitude recovers toward the extreme again, and Yang Gu is then needed to turn the user around and cut aptitude by ten percent once more. ^{ch. 199} Destroying the pair would leave Bai Ning Bing unable to return to a male body. ^{ch. 201} The Gu that saved Bai Ning Bing does not resurrect the Gu worms lost when those worms froze to death. ^{ch. 200}

If Yin Gu and Yang Gu are intact and form a complete Taiji light sphere, they feed on the transformation of yin and yang qi and are self-sufficient. With only Yang Gu left, Fang Yuan must release it to absorb yang qi in the air. ^{ch. 202}

When Bai Ning Bing’s Northern Dark Ice Soul Physique is about to finish killing its host after self-explosion of both arms, Fang Yuan activates Yin Gu from the pair and merges it into the ice sculpture. Bai Ning Bing breaks free alive, no longer holding that ten extreme physique, at ninety percent aptitude instead of one hundred. Fang Yuan keeps Yang Gu refined in his aperture and can order it to self-destroy, which is the hold he uses after the crisis. ^{ch. 199 ch. 201}

In Shang clan city, Fang Yuan tells Bai Ning Bing to ask Doctor Su Shou about Yin Yang Rotation Gu, and Bai Ning Bing does ask about it rather than ask for healing. ^{ch. 271} Bai Ning Bing states that she already has yin yang rotation Gu, but needs to advance it to immortal level before she can reverse the female body, and that it is not her vital Gu so she lacks confidence in that refinement. ^{ch. 1380} She later allies with Fang Yuan toward refining immortal level yin yang rotation Gu, including a plan to use Lang Ya Sect contribution points for a refinement mission. ^{ch. 1462}

When Fang Yuan cannot use several Gu in northern plains, he leaves yin yang rotation Gu in Hu Immortal blessed land with Blood Skull Gu, Bone Flesh Unity Gu, and other Gu not useful at that moment. ^{ch. 504} The yang Gu left after using yin Gu of the yin-yang rotation Gu is still there, beside rank four Blood Skull Gu and rank three Bone Flesh Unity Gu. ^{ch. 581} As an immortal zombie, Fang Yuan notes that yin-yang rotation Gu is only rank four and would not restore his human body. ^{ch. 653}