If it were just a regular spirit stone mine, the Netherworld Sect would indeed not care. Even with the Chu Family mining it, they'd have to turn over half of the mined spirit stones to the Netherworld Sect.
But beneath this mine, there is also a hidden vein of Divine Crystal.
According to the rules jointly established by the various forces in the Quicksand Divine Domain, the Chu Family can keep half of any resources they mine, even if they find something as valuable as a Divine Crystal.
How could the Netherworld Sect be willing to let the Chu Family, a Second Grade force, obtain half of a Divine Crystal vein?
As for whether intercepting and killing all members of the Chu Family Camp would cause turmoil in the Quicksand Divine Domain's gathering area or even the entire domain, the Netherworld Sect already had a plan.
