From the advice of Will Kris, the Snake of Fate, Klein keenly picked out the key point: they needed to find "survivors of the old era" like Angel and himself to enter the dream.
This would make it easier for those entering the dream to communicate, preventing disagreements caused by differences in their ways of thinking. It would also keep Angel Granger's dream from having too great an impact on people of this era.
After all, judging by Angel Gray's experience, this real dream would most likely display the parts most deeply etched in its owner's memory—the surroundings in which she had lived in her "previous life."
Of course, besides being survivors of the old era, possessing the status of a True God or the protection of a sefirah was also essential. This would prevent them from being corrupted by the City of Calamity or the River of Eternal Darkness upon entering the dream, or losing control because of the Original Creator's power.
Few candidates met both conditions: the recently revived Black Emperor, Roselle Gustav; the fellow transmigrator and True Creator, Grisha Adam; and, of course, the Evernight Goddess, Amanises, who had agreed to help from the very beginning, as well as Angel Gray and Klein himself.
As for Farbauti, the Devil Monarch who was also a transmigrator, Klein had not invited him. First, Klein did not know him well enough to feel comfortable letting him enter Angel's dream. Second, this deity was in poor condition and had even needed to split off an Abomination avatar to reduce God Almighty's and the Outer Deities' influence on him. He probably had no strength to spare.
Apart from him, all our surviving "fellow countrymen" are gathered here. Fate really is marvelous... Klein mused. When he saw the shadows completely recede from Roselle