An inner demon is created from stubborn thoughts.
Once an inner demon appears, the cultivator would be affected. Especially during the cultivator's breakthrough, the inner demon likes to come out and stand in the way of the cultivator's breakthrough. So much so that the cultivator may even die from it.
This was what was happening to Ling Xian.
When he was about to have his breakthrough just now, the unforgettable image in his mind came back, which meant the suppressed inner demon was making a comeback. The moment his inner demon came out, his face turned pale and he puked out a mouthful of fresh blood.
From this, it became obvious just how terrifying it is when the inner demon explodes.