UWE HNO+FN Alliance
Universal Wasteland Expansion added a 50 relation boost from the Holy Nation Outlaws side so they view the Flotsam Ninjas as allies, but this is not reciprocated. This mod adds an equal relation boost on the Flotsam Ninja side. Ideally this will prevent infighting when the two meet at your base to defend against the Holy Nation.
This mod does not actually require UWE, it was just made with that in mind.
