Fang Ning had experienced the difficulties of a Saint. The being they had sent in was not of a physical nature and instead, it should be called "Demonic Sense", or something along the lines of such illusory things.
It could capture one's heart and make one do things that seem fitting, but in reality, were unreasonable things.
For example, in the face of a benefit, most people would be able to resist the temptation. However, once Demonic Sense arose in one's mind, one would feel confident enough to do illogical and irrational things.
Although he had the power to control the Heavenly Axiom, the Heavenly Axiom was unable to interfere with the hearts of people, let alone control them.
Unless he killed all living creatures in the world, Demonic Sense would never perish.
Moving mountains would be easier than moving the hearts of people.
These Saints were truly meticulous too by aiming the strategic points the moment they attacked.