Nu Ba is the Goddess of Drought and is said to be the daughter of the Yellow Emperor (黄帝 huáng dì).
According to the Classic of Mountains and Seas (山海经 shān hǎi jīng), in the battle of Chi You (蚩尤 chī yóu) and the Yellow Emperor, Chi You called upon Feng Bo (风波 fēng bó) and Yu Shi (雨师 yǔ shī) (the Gods of Wind and Rain, respectively) to deal with Ying Long (应龙 yīng lóng), a celestial dragon with wings that could control the rain, that was fighting alongside the Yellow Emperor.
To counter their combined strengths, the Yellow Emperor requested the assistance of Nu Ba who was able to push back the heavy storms created by Feng Bo and Yu Shi.
In the end, the Yellow Emperor and his armies were triumphant.
Nu Ba and Han Ba
To this day there is still a lot of debate as to whether or not Nu Ba and Han Ba (旱魃 hàn bá) are the same person. Despite where you stand on this debate, it cannot be denied that there are many similarities between the two.
Version 1: Nu Ba was originally a goddess, but after the Battle of Zhuo Lu (涿鹿之战 zhuō lù zhī zhàn), she was denied to return to Heaven. Over time, she gradually lost her mind and changed into Han Ba.
Version 2: Nu Ba sacrificed herself to save Ying Long. Her Hun and Po1 split and she turned into Han Ba.