With such a bizarre transformation, Ren could only treat his Emperor Weapon, the Zhu Xian Sword Formation, as an upper-grade Houtian Spirit Treasure!
Of course, Ren knew that if he improved the Zhu Xian Sword Formation's quality, turning it into a supreme-grade Houtian Spirit Treasure would be easy!
But replacing the materials in an already completed Spirit Treasure required profound mastery of the Artifact Refining Art. At Ren's current level, he had no hope of doing it!
Yun Zhongzi could do it, but Ren had no intention of exposing his secrets, so he would never hand it over to him!
The other option was to give the Zhu Xian Sword Formation's divine spirit precious materials and let it digest and devour them, reshape itself, and slowly improve its own quality. Unfortunately, the Innate materials of the Primordial World were not easy to absorb. The process would be very, very slow...
With no better choice, Ren could only keep honing his Artifact Refining Art before trying to improve the quality of those Emperor Weapons!
Then again, judged by quality alone, a middle-grade Houtian Spirit Treasure from the Primordial World could rival an Emperor Weapon. The power it could unleash was only slightly weaker than the Zhu Xian Sword Formation!
After all, in the Shrouding the Heavens World, the Zhu Xian Sword Formation ranked among the foremost Emperor Weapons!
By the same reasoning, although a middle-grade Spirit Treasure had no divine spirit or Great Emperor's Great Dao condensed within it, its quality alone should let it rival the weaker Emperor Weapons of the Shrouding the Heavens World, such as the Black-Gold Dragon-Pattern Cauldron and the Jiuli Diagram!
Tu Fei's grandfather would surely agree to trade half of the Devouring Heaven Demonic Jar for a Spirit Treasure comparable to the Black-Gold Dragon-Pattern Cauldron!