The Heart of Eternity was really filled with extremely pure light essence, and used the blood vessels of the original Scion of Light, Elux. Long Haochen being a Scion of Light too, his blood vessels joined with the former Scion of Light’s, although a short time of rejection had occurred first.
In the contest of blood vessels power, Long Haochen was far more powerful, after all Elux had already deceased several thousand years ago. Perhaps his spiritual energy did not come loose, and was still as incredibly powerful, but his blood vessels had already long since decayed. He could only extract the best parts of the blood vessels, which was why after this short time of rejection and clashing, Long Haochen’s own blood vessels took complete control and were the ones to integrate this blood vessel power of great purity.
