Qixia Mountain, Black Wind Village.
This place was originally a military camp abandoned by the government army, taken over by a group of strong-men who managed the area and it became the now-famous Black Wind Village of Jiangning Prefecture.
The leader of the strong-men is also skilled in military affairs. On the seven passes leading to Black Wind Village from Qixia Mountain, small fortresses were built to guard the main roads. Only several tens to a hundred people are needed to hold them, and even thousands of official soldiers can't hope to break through them.
Such chokepoints amount to seven altogether, and it's unknown how many lives would be lost trying to conquer them.
Not to mention Jiangning Prefecture, even Yingtian Prefecture, being the capital of South Zhili, does not have the financial power.
Thus, both high and low officials of Jiangning Prefecture have just let the matter be.