The One Ring: Fellowship of the New Alliance
The narrow belt of land flanking both sides of the River Running where it touches the eastern eaves of Mirkwood has been turned into a trackless swampland by the flooding of the river waters over too many years to count. But in more recent times, relentless rains and even a couple of earthquakes have seen the Long Marshes expand their boundaries north, to reach and engulf even the course of the Forest River where it exits Mirkwood to the east. By 2946, the Long Marshes cover an area more than one hundred miles long from north to south, from the eastern borders of the Woodland Realm to the shores of the Long Lake, and south beyond the Mountains of Mirkwood.
To enter the Long Marshes, a traveller needs only follow the River Running as it goes south beyond the Long Lake, or the Forest River to the west. Often, the marshes will offer the same sight, regardless of the chosen direction: a wide, treeless expanse of mires and pools of sullen waters, unmoving but for the river course that stirs them. Here, thick mists rise in the morning, and lift only with the approaching of midday. But the fog never really disappears; rather it changes into a transparent vapour, capable of turning the brightest light of the Sun into the palest radiance.
The dreariness of the region is multiplied where the marshes meet Mirkwood. Under the shadows of the forest all sounds of nature are utterly silenced and only chill breezes move the drooping branches of the trees that rise from the waters.