In this Star Palace, the heaven destroying Army was relatively weak. Moreover, after the incident where Lu Ming killed many cultivators of the heavenly human tribe, Tian Xuanzang was sure that the heavenly human tribe would not let them off.
They would definitely search for the sky destroying Army in secret. If this went on, they would be in a very dangerous situation.
Therefore, Tian Xuanzang wanted to bring people to seek refuge with Lu Ming.
There was another reason. Lu Ming and the others occupied a high-level earth vein. If they could join Lu Ming and enter the high-level earth vein, the speed at which they condensed the desolate pill would increase exponentially.
The further one advanced in the celestial Thearch realm, the more desolate pills one would need to make a breakthrough.