Because the Drought Demon was parasitized by the skull of the dead Pangu and turned into a zombie. It is the earliest zombie, the same as Yinggou, Houqing, and General. Also known as the ancestor of the four zombies. So Hanbao is the ancestor of zombies. (Ying Gou, Hou Qing, and Nv Ba are the souls of Jian, and the generals are the body of Jian + the sacred tree).
The detailed legend is as follows:
Pangu died of exhaustion after creating the world. After Pangu died, Pangu’s left brain turned into Fuxi, his right brain turned into Nuwa, and his heart turned into Hao The sky, and the skull turned into Jian. Jian, as the skull of Pangu, has the hardest and most powerful body, and it harms the human world.
Afterwards, Fuxi and Nuwa teamed up to defeat Jian. They separated Jian's soul from his body, divided Jian's soul into three parts, and sealed them together with Jian's body. However, Jian's three souls broke through the seal one after another and merged with Yinggou, Houqing and Nuba respectively, turning them into zombies.
But Jian’s body obtained branches of a sacred tree from Haotian and fused them to form a new zombie general.
Extended information
The story before Drought Ban turned into a zombie:
Ban was first a goddess, a god, the daughter of the Yellow Emperor. When the Yellow Emperor and Chi You fought, the Yellow Emperor sent Yinglong and Tiannu Ba participated in the battle. Ba was wearing green clothes and could emit light and heat. She came to the front of the battle and exerted her magical power. The wind, rain and fog immediately dissipated, and Huang Di finally captured and killed Chi You.
Yinglong and Ba established extraordinary achievements, but they also lost their divine power and could never return to heaven. Yinglong stayed in the south of the human world. From then on, the south had lots of water and rain.
Ba stayed in the north. From then on, there was a drought in the north. No matter where she went, she was cursed and expelled by people.
The image of the Hanba from the Pre-Qin Dynasty to the Han Dynasty is represented by the image of the goddess, whose image is characterized by a woman wearing green clothes. During this period, the Drought Demon had dual identities of gods and monsters. People regarded it as the God of Drought, but they also used methods such as sun exposure, flooding, and tiger food to drive it away in order to drive away drought and seek rain.
From the middle and late Han Dynasty to the early Ming Dynasty, the Hanba in the image of the goddess gradually transitioned to the Hanba in the image of another imp. The reason for this change is that the worship of nature gods that was prevalent in the Pre-Qin period gradually declined during the Han Dynasty.
The divine side of Hanba was gradually denied by people, and her female identity was also questioned. After the mid-Ming Dynasty, the Hanba with the image of an imp gradually evolved into the Hanba with the image of a zombie (parasitized by a dog), and was gradually replaced by the Hanba with the image of a zombie.