"Except for those who contain the blood of gods and demons, any cultivation by any other soul will face backlash and be swallowed up by the summoned demons. The value of cultivation is zero."
The cultivation by souls of non-demon descendants wouldn't be recognized by the summoned souls.
This also explained the story of how Buddha practiced so much but still faced a backlash at the end.
Then why could he do it? Su Yu thought about it. He got three drops of blood belonging to the gods and demons and merged them inside the Divine Nine-Dragon Cauldron before they were finally integrated back into Su Yu's blood. Is this why he did not face a backlash?
"If you have enough blood of the demon, you should be able to use [Sacred Demon Summon] without any problems," Su Yu thought to himself.