Normally, when an ordinary person is contaminated with yin-toxic qi, there is only one possibility: they have had very intimate contact with a dead person.
Moreover, that dead person was no ordinary corpse, but someone who had undergone extraordinary experiences during their lifetime.
Because a relatively large amount of toxins remained in the body after death, combined with the fact that the corpse had not decomposed or rotted over a long period, the toxins and yin-cold qi condensed and fused together to form yin-toxic qi.
Chapter 205