In fact, even if Qin Yun did not protect the mortals, it was unlikely that Palatial Lord Kuishi would pulverize the surroundings! Although the fiendish way was evil, most Skyfiends were still concerned with karma.
Once their sins reached the state of giving them a Sinful Sanguine Halo, they had to be more careful.
If they went one step further…
The sins would result in Negative Karma Fire! Most Skyfiends would die under Negative Karma Fire.