The Emperor of Demonic Beings is very special; his level of power far surpasses that of the top Jade Immortals.
After all, the demonic creatures are but a condensation of a wisp of Demonic Qi from the Ancestor of the Demon Abyss.
And the Emperor of Demonic Beings is the ultimate form born from the endless sea of demonic creatures.
It's not an exaggeration to say that he is an incarnation of the Ancestor of the Demon Abyss.
Therefore,
In the numerous wars between Immortals and Demons, what the Immortals of the Immortal Realm dread the most is the Emperor of Demonic Beings.
As for the ordinary demonic creatures?
Even in endless numbers, they could not possibly breach the defense formations of the great Immortal Cities.
As long as they endure until the passage to the Demon Abyss dissipates, that will be enough.