Nalan Shan had similarly detected the abnormality. He had researched into the Serene Spirit Tower for so long and no one knew the dangers of the Serene Spirit Tower more that he did.
According to Nalan Shan's investigation, once one's power of the spirit was raised to a certain peak, they would disappear, and those spirit souls who had disappeared could very possibly have become sacrificial victims of the enormous Spirit Fire on the twelfth level.
From the looks of Jiang Yun Long's powers today, Nalan Shan was guessing that the time of Jiang Yun Long's "disappearance" would not be much further off.
The Serene Spirit Tower was not a place for cultivation at all, but a slaughterhouse instead. For all the human spirits cultivating in there, they were just like meatstock reared within the Serene Spirit Tower, waiting till their powers become sufficient before they became the Spirit Fire's "food".