"Stop it! He's your son!", Nie Dao's wife cried out pitifully while being held back by a few guards. The patriarch turned a deaf ear to his wife's pleas and proceeded with the ritual.
There were a few magicians, who believed in magic instead of soul power and cultivation, which had played an important role during the ritual. The patriarch hired a few of them in order for the ritual to be carried out successfully.
While his son was being bathed in blood, the magicians were chanting mantras that would help the child to gain a Hell-Hound Cerberus.
Although this ritual might be helpful for the clan, the magicians were actually risking their jobs and lives.
This ritual involved the darkest black magic there was, which was banned on the whole continent. If it wasn't for the handsome pay they were given, the magicians wouldn't have fulfilled Nie Dao's requests.
Fortunately, Nie Dao's son, Nie Shao did obtain a similar beast soul, which was a 2 headed dog.
Next info, in chap 100