This is the point of a 'Hive World' like Necromunda, to be a manufacturing center to provide equipment for the boundless legions of the Imperial Guard and Space Marines, as well as lay down new hulls for the Imperial Navy.
After fighting him off, and discovering that the Bloodmare Stone (An eye from one of the- if not the- last of the Giant Necromunda Spiders) is the source of his great power, Klovis and his band set out deeper into the Underhive to purge the Caller.