Within Lin Mu's body, a change was happening.
The layer of impurities that had been merged with the dantian was being forcefully separated from it. This was being done by pushing out the spirit qi wisps from the dantian. Instead of letting them pass into the meridians like normally, Lin Mu was pushing them out of the pores in his dantian.
If someone else were to try this, they would likely cripple their dantian forever or even explode it. But because of Lin Mu's saturated vitality, the damage was being repaired just as it was being caused. Large beads of sweat appeared on Lin Mu's forehead, and he bore through the pain.
This was no easy task and many would have given up a long time ago. But with Lin Mu's own determination and the assistance of the severing heart sutra, he held on. Finally, the layer of impurities cracked like the shell of a hard boiled egg and a burst of spirit qi came out of the dantian.