Yale knew that although the seven-colored light could make the process of creating an Essence easier, it didn't change the fact that faith was a need.
Shiba had a piece of the legacy of the universe creator and was also quite famous, so he met the basic conditions.
Yale didn't know who the last person was, but he didn't doubt that besides the fact that the other person hid, he should have some reputation to be able to obtain faith from others.
Moreover, that person should be like the Battle God or like Yale. In other words, it should be someone who ascended from other universe or with a piece of the universe creator's legacy.
There were only five pieces of the universe creator legacy, and Yale knew three of the inheritors, which with himself included made four.
As for the fifth, no one knew about him. Even when the pieces of legacy resonated in the past, the fifth person remained hidden, and no one managed to notice who was.