In ancient times, the Heavenly Emperor opened the Gate of Firmament, connecting the Heavens and Earth. Even mortals could learn to ascend to the Gate to meet with the Emperor and to obtain divine powers in order to aid the mortal realm. Unscrupulous individuals took advantage of the Emperor's gesture, and plunged the human realm into chaos, filling the lives of the common folk with anxiety and weariness. At this time, the sibling gods Fuxi and Nüwa took pity on the people and convinced the Queen of Huaxu to close the Gate forcibly with the help of Emperor Zhuanxu. From then on, no one could reach the Heavens with impunity, and no god could travel to the mortal realm freely. This incident came to be known as the Isolation of the Heavens and Earth.

Spin-off of the game 軒轅劍外傳穹之扉(The Gate of Firmament)