More specifically, I'm trying to remove the Chaos Corruption created by the Gorebull and Bray-Shaman agents. This is a fairly personal change, as my friend and I found that playing Cooperatively was a bit difficult when I spread 8 to 15 Corruption to his lands by simply being in an adjacent province fighting his enemies.

So far, I've managed to remove the Corruption spread from the Beastmen's Main Building chain, Tech Tree and City Ruins(Totems). Leaving the Beastmen Agents as the only cause of corruption spread left, and I've had difficulty figuring out how to change their values so that they don't do it anymore.
Any help would be appreciated.