"As long as you all do not die, and the Demon Banner remains unextinguished," said Taiyi, "when my elder brother and I return, we shall revive our Demon Clan brethren and reappear among the human world."
Taiyi spoke and told the ten great demon gods to leave this place. As for the demons below, Taiyi didn't care at all, because demons are undying.
The primary function of the Demon Clan's treasure, the Demon Banner, was not just to command all demons, but to resurrect the dead demons.
The function of the Demon Banner, similar to the Investiture of the Gods, was merely to entrust a wisp of one's True Spirit upon it. Should an accidental demise occur, one could be resurrected by relying on the True Spirit imprint left on it.
This was why countless demons willingly handed over a wisp of their True Spirit for Di Jun to refine the Demon Banner.
Once the True Spirit entered the Demon Banner, one could become immortal and indestructible. Who could refuse such an offer?