As time passed, the technology of Gu cultivation among the people of Miaojiang improved continuously, evolving from a mere means of self-defense to a tool that could control one's mind or directly cause death.
Types of Gu bugs raised by someone like Tuotuo, whether it's the Golden Silkworm Gu, Lice Gu, or Gu bugs like ants and locusts, all required the raising of a Gu King. When deploying the Gu, one usually had to flick their finger out, with distinctions made between one, two, three, or four fingers. Gu bugs released with one or two fingers are easier to treat, and the affected can recover relatively easily. For instance, when she just applied the Gu to Li Ruizhu, she flicked her second finger.
But Gu bugs released with three fingers are much harder to treat, and those released with four fingers are Deadly Gu, which even the caster cannot resolve, let alone Immortals and Bodhisattvas.
