Speculation to DTB S2, ep 2,3.
I havent read in here, yet but will do it afterwards.
Hei's star fell. I think and if i remember correct, it was never his star. It was the star of his sister, Pai, who always have been "in" Hei. So basicly, Pai got killed. Thats why the star fell and (it looks like) Hei lost his contractor abilities.
I think other people may have thought the same but not sure, if this makes realy sense.
