Chen Mobai immediately thought of the "Sword Fiend Collection" he had obtained from Taoist Master Zuo Gong, the head of the Swordsmanship Department at the Refining Department, when he heard the term "Mysterious Yin Fiend."

Within the Immortal Gate, due to the near extinction of the Earth Fiend Qi, supernatural spells like the Sword Fiend had mostly become ornamental.

Because of this, the "Sword Fiend Collection" compiled by Zuo Gong and several experts from the Swordsmanship Association was purely a display of skill, with no practical application.

Chen Mobai had been so busy improving his Pure Yang Scripture over the past two years that he had almost forgotten about it.