Degree of Interference
Yale's incarnation moved through the shadows without letting the people residing in that world notice his existence.
He had the idea of betting to make his incarnation reach that world for two factors.
One of them was Tofesh, who managed to appear again in front of him although he had possessed a body to do it. Moreover, he seemed to have a lot of restrictions.
The other was the Mysterious Expert. Yale didn't know even the gender of that person, but its incarnation seemed to be always near in the shadows, and there was no way to know how many incarnations that person through the universe had because Yale didn't believe that there was only one as it seemed to be always near him.
Thus, Yale decided that if he sent and incarnation and hid it in his disciple's soul, there shouldn't be too many problems for going into a lower universe.
After all, if no one noticed his presence, there shouldn't be too much effect on his existence there.