Pitch Black Gu

It is oval and black like a yuhua stone, with seven white markings on the surface, peculiar and dark. ^{ch. 380}

After Wu Gui dies, Fang Yuan finds Wu Gui’s one rank five Gu: oval and black like a yuhua stone, with seven white markings on the surface, peculiar and dark. Once activated it oozes black smoke; any Gu worms below rank six contaminated by that smoke receive various degrees of sealing and lose their abilities. Fang Yuan notes Wu Gui’s other rank four Gu are mixed among different paths and not a complete set, judges that Wu Gui can roam southern border mostly because of this Gu, calls it an extremely useful rank five Gu, and keeps it in his aperture. ^{ch. 380}

Against a swamp crab desolate beast, Fang Yuan still holds pitch black Gu among other rank five Gu such as turn gold Gu and Soft Bones Gu, yet using them would be like throwing pebbles in a lake and would only create slight ripples without continuous attack. ^{ch. 417}

He leaves pitch black Gu in Hu Immortal blessed land with other Gu he cannot use at the time, including vajra stare Gu, turn gold Gu, blood skull Gu, Bone Flesh Unity Gu, and yin yang rotation Gu. ^{ch. 504}

Later ranking talk groups rank five pitch black Gu with rank four problem nipped in the bud Gu as Gu that target a Gu Master’s worms, then says the killer move thirty-eight sealing arts is much stronger than pitch black Gu. That killer move can contaminate moves a Gu Master uses and seal the Gu worms for those moves one after another. ^{ch. 642}