To Thousand Sails City, the northern Poison Fog Canyon was a true deathly forbidden area. Not only was it filled with a deadly fog all year long, but it also harbored the biggest underground force of Thousand Sails City, the Viper Nest.
Even the Monchi Family, which supported the Viper Nest, didn't understand why a major force would occupy such a barren land with poor ore veins and poison constantly spreading all about. Moreover, there were all kinds of dangerous magic beasts hidden within the poison fog. This was the state of the Poison Fog Canyon.
Among the territories occupied by all the various major forces of Thousand Sails City, even if the Viper Nest's Poison Fog Canyon wasn't the very worst one, it was definitely among the worst ones.
There was simply no way that such a place could bring in much profit. Moreover, in order to resist the assault of the magic beasts, the Viper Nest would have to keep a lot of manpower tied up every year.