Soft Bones Gu

Ku Mo had eight Gu worms and only one rank five Gu, soft bones Gu. Even if Fang Yuan turned his bones into essence iron bones, he would still be affected and his bones would turn soft eventually, leaving him unable to fight back. Without a skeleton for support he would lie paralyzed, with organs and vessels clogging, and die before long even without further attacks. Fang Yuan takes the Gu and keeps it for now, noting he does not know much about bone path. ^{ch. 380}

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