Strangely, after the Black Heavenly Spirit was born, it no longer absorbed Heavenly Spirits. The discovery made Xu Yi click his tongue in secret. If he followed this reasoning, then the Purple Heavenly Spirit and Gold Heavenly Spirit must be things born naturally.
Xu Yi then tried releasing the Cloud Crane Pure Qi and placing the Black Heavenly Spirit in the Purple Domain Space. To his surprise, he found that the Black Heavenly Spirit no longer decomposed either, instead displaying an unusual stability.
After studying it for a while without understanding why, Xu Yi felt the restlessness in his heart flare up completely. He had been imagining what sort of effects a Black Spirit-level magic treasure might have.
The restless urge flickered and then died away. Without a method of refining it—and especially without knowing how to outline the Law Pattern channels—he could not proceed, even with the Purple Domain Space allowing ample room for error.
Now that this wish had taken root in his heart, he no longer wanted to refine any other treasures.
As for the Bixiu Sword, he had merely restored it and no longer planned to fuse it with a Heavenly Spirit. With his current cultivation and the battles he was about to face, the Bixiu Sword was already beneath him.
Still, the Bixiu Sword itself was a fine divine weapon. Given to Yan Zi, it would let her dominate a corner of the world at her level.
For now, Xu Yi stored all the Heavenly Spirits in his Starry Sky Ring. He had no plans to keep fusing them into Black Heavenly Spirits; after all, the process was irreversible, and he might need the Heavenly Spirits someday. He could wait to fuse them until he found a way to refine a Black Spirit magic treasure.