C1736 Ninth Stage of the Heavenly Road
Xue Zhantian broke out of the shackle and his soul was reborn, hence the quality had dropped quite a bit.
Their souls were very evolved, but the only exception was the Master of the Universe. Therefore, every single one of the Universe Overlords had a much higher quality soul than Xue Zhantian, but no matter how high quality they were, they were still unable to open the door to the Immortal Soul