“ A group of Mages sought to create an Elixir of Fertility, to deal with the Curse of the Empty Cradle. After acquiring such things as the 'ahem' vigor of a war deity, and the 'ahem' blessing of a forest goddess, the mages almost created the cure. Instead, the vessel of Divine Virility was spilled, and instead of curing sterility, infused the ancient hill with life. The temple and alter rose, becoming a demonic force of life essence and the fecundity of nature.”
“ 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.”
“ You find a patch of edible funghi. They taste well and all, no ill effects. UNLESS you consume some beverage, even 3 (three) days after eating it. Then you become really sick with pains, vomiting, all the fancy stuff. As a gift or good meal, it could be a cruel joke or to make sure the heroes spend their time focused on the mission. And the fine soup you had in the inn yesterday could have some in.
(Inspired through a real-world fungus. Was really used to cure alcoholism.)”