After realizing that the situation was dire, Yan Fei did not panic but instead calmly analyzed and thought through the problem, eventually discovering an issue. Although the cosmic human souls are powerful, the space in which these soul entities operate is very limited. They can only function near the site of their death and cannot stray far.
For example, the old ghost that wanted to possess Tripiṭaka earlier was also a cosmic human soul entity. It could only remain in that underground cave and could not leave. It wasn't until Tripiṭaka was buried underground and in a coma that it seized the opportunity to enter Tripiṭaka's mind. If that cosmic human soul could leave the underground cave, it would have found a body to possess long ago and would not have needed to wait eighty thousand years there.
