War
The moment the Metal Work Sect's territory was encroached upon, they took it as a declaration of war, and that it was. There were only so many resources to go around, how could they just casually allow anyone to appear so close? In fact, the sudden manifestation of the Radiant Star Sect actually caused a lot of those resources to be buried beneath a pile of rubble.
Their Metal Work Sect followed both the path of blacksmithing and Body Realm cultivation. They placed a lot of importance on the earth and the ore veins hidden within, and just now, the Radiant Star Sect had landed on, precisely, one of their veins.
The worst part was that the appearance of the Sect had definitely slaughtered everyone that had been working the mine. This included disciples working for merits. With their manifestation, the Radiant Star Sect had already slaughtered their people. How could this be tolerated?