The Favánë is an subterranean river that has its headwaters the northern tip of lake Pargemor. It also sees drainage from Orondir, a surface swamp. Going north, the river cuts through the Sigan-Kûn cavern. In this area it is flanked by a fungal forest called Erochel. In this area near farmlands once tended by Mulun-Dûna, the river is tainted by experiments with alien pixie dust, for increasing plant yields and the number of Myconid available to farm.
Periodically, feywild fuses open in or near this river. They are the result of experiments using alien pixie dust. Many of the alien plants, critters, and creatures roaming the river's banks or swimming along it, are natives of the faraway world Kriav . Another side effect of the pixie dust was the sterilizing of the locale Myconid population. Today, those encountered across Greroch are descendants of those that came over from Kriav, or recent arrivals.