Tang Ye had learned about the Gu poison from Tang Manhong, such as the Living Gu, a rare and strange poison. The Miao Jiang witch, Cao Guipo, could infuse the Gu, which fell into two categories, the Dead Gu and the Living Gu. Dead Gu were more common, delivered silently through various media, like poisonous scorpions, butterflies, or plants. The Living Gu, however, were rarely seen due to the difficulty of their creation; they required the witch's mastery of witchcraft and an advanced proficiency in Gu poison skills to control the poison at will.