When Lilith left Bai did he not feel slightly betrayed about her leaving and lost some of the closeness he felt with her or did that get washed away with how Bing has gotten closer to him, affecting the stone heart? I remember reading that right after Lilith left a while ago…
It still hasn't been explained how they knew where Earth was. Let alone why they can't interact or observe Earth. Maybe Earth is the birthplace/home world of Medes, Lucifer, and Fire Sorrow?