Chen Heng's goal in creating the Holy Son clone was to take in that massive amount of faith energy, as well as to avoid being affected by the faith energy.
This way, the one who would be affected was the Holy Son clone, not himself.
The divine energy that the clone processed would then be sent to Chen Heng for him to use.
Of course, this process had its limit; most of the energy remained within the Holy Son clone.
Before, when Chen Heng had fought with the Origin Curse, most of the energy he had used was from the Holy Son clone.
As time went on, the Holy Son clone had gathered a massive amount of energy.
This was especially so after Chen Heng gained more and more followers, causing more people to believe in the Holy Son.
This was very good for Chen Heng.
However, by now, the effects from the faith energy became quite evident.