Changing potion parameters.

I can't say for sure, but it seems there are separate files for the random map generator. They contain parameters for the terrain, what types of structures will appear, and what creatures will guard them, as well as duplicated characteristics of resource nodes. I repeat, I cannot guarantee the accuracy of this information. It's all approximate and based on memory, so it might be completely wrong. But if these preset files exist, you should look for them in the folders/subfolders with the name RMG, i.e., random map generator.