The Heavenly Demons of that era must have been annihilated by the Sixth Generation Immortal. Today's Heavenly Demons are likely just beings who have inherited the Heavenly Demon bloodline and awakened it. They are not true Heavenly Demons, but rather individuals who possess the power of a Heavenly Demon, or perhaps... other kinds of demons? Now, it seems they are colluding with the several major dynasties of Li State, seeking to stir up chaos there.
The Ice Blue Ancient Tree explained why these Heavenly Demons act this way: they cultivate not by relying on Heaven and Earth Spiritual Qi, but on Karma. The heavier the Karma in this world, the stronger their powers become. If Li State is too peaceful, there naturally isn't much Karma; the more chaotic the world, the stronger they become.
This power plaguing the Desert Sea Plain... it must be the Golden Crow Demon Flame of the Heavenly Demon Drought Crown... Just a wisp of it is enough to plunge the entire land into a fiery drought.
