If there was only one type of poison, they could resist it with their profound cultivation. If they discovered it in time and expelled it from their bodies, it would not cause too much harm.
The key was that the red silk that was used to decorate the Five Poison Sect also carried a colorless and odorless poisonous gas. When all of these were combined together, they formed an extremely powerful poison that was hard to detect in the body. Even Yao Tianchen had been fooled.
These were all specially developed by the Five Poison Sect's ancestor to counter them. Once spiritual power was used, the blood would flow in reverse and the poison would quickly kill them. Most of the people from the Wind Thunder Pavilion died due to this.
"Everyone, listen to me. Do not use your spiritual power again. Otherwise, the poison will also travel to your internal organs. When that time comes, even the gods can not save you."