Ye Manman

The heroine and her younger sister were elected to the palace one after another. The elder sister became the concubine and the younger sister became a maid. Later, all the concubines discovered that the emperor was possessed by evil spirits. They practiced immortality in the mountains and successfully rescued the emperor who was basically possessed by the devil. Later, because they could not live a normal life with humans, they turned into spiritual beasts and returned to live in the mountain streams (see my story for details!)