First: Li Qing
Second: the mysterious Fate-less, whose existence they had known about for over ten thousand years, yet never captured.
After careful comparison, the Eight Immortals increasingly leaned toward Li Qing being the source of the threat.
Hearing this, Wan Jie Demon Lord reported the strange death of Bai Mo to the other seven. He too suspected Li Qing's involvement, since the other Fate-less had long completed the cultivation of the Five Divine Repositories and had no reason to steal from Bai Mo.
If Li Qing had truly obtained a rule seed, then the time for his Divine Soul Tribulation was near. For that, he would require a grand enough battlefield to ascend to the Supreme Divine Soul.