Qin Changqing had already established several cave dwellings on Taixuan Peak, capable of accommodating millions of members of the Qin family.
This was a precautionary measure.
Demonic cultivators weren't known for playing by the rules.
Taixuan Peak was safeguarded by the Yuan Magnetic Barrier, which deterred the demonic cultivators.
Qin Changqing had already defended against his enemies twice through the Yuan Magnetic Barrier.
However, no wall was ever completely airtight.
If the demonic cultivators attacked again, they certainly wouldn't be fooled as easily.
Therefore, from Qin Changqing's perspective, these attackers were likely to strike at his descendants first in an attempt to draw him towards the outskirts of Luo City, where they could deal with him directly.
While Qin Changqing was strong enough not to fear them, he had to be prepared for any eventuality.