Actually, the reason was to do with Chen Wuhui and Zhu Lanhuo. Two months ago, Chen Wuhui had gone to explore the Tan Zi Beast Lair and had accidentally discovered a mysterious treasure. Originally, Chen Wuhui had planned to furtively remove the treasure but had discovered it was no easy task. After a great deal of trouble, not only had he failed but both he and a few Intentionless Sect elders had been injured.
Of course, that was just the beginning of the story. Later, for some unknown reason, Sacred Flame Sect must have found out about the discovery too. The two sect leaders led a team, ambushing the people from Intentionless Sect while they were returning to Intentionless City. They were already injured and so were no match for their well-prepared opponents from Sacred Flame Sect. Two Intentionless Sect elders died on the spot and Chen Wuhui was also heavily injured. He gave up on obtaining the treasure and returned to Intentionless Sect.