This is an editted version of an article I did many years ago covering the basic information about sake.
Some guidelines on making workable martial art styles within a game.
Twenty questions to help create a cult.
Real World: some Indians in the Amazon treat their eyes with a traditional potion applied with palm leaves. Brutally painful, the drug alters vision, giving the jungle's dense green walls greater texture and dimension. You could adapt this to desert or swamps, or other hard to navigate regions.