The Yin Yang Refining Immortal Mirror was a Defining Treasure of the Middle Continent Ancient Kingdom.
The Yin Yang Refining Immortal Mirror was secretly brought from the Middle Continent Ancient Kingdom by Middle Continent Princess. It was buried with her in the Ancient Heavenly Corpse Burial Ground and remained there for millions of years.
In the Current Era Li Qiye visited Middle Continent Princess. He used three Corpse Treasures and information of Chu Yuntian's place of burial to trade with her for the Yin Yang Refining Immortal Mirror.
It can halt attack of any Immortal Emperor Life Treasure. Ten Worlds Yin Yang Fish Citadel, is the ultimate blow of the Yin Yang Immortal Refinement Mirror, a wondrous defensive line.