A sluggish, turbid waterway that drains into the Misty Marshes from the northwest, the dark twin of the Sweet Water River. Where the Sweet Water runs too fast for the fog to settle in it, Mud Run barely moves at all, and the mist has soaked all the way through. The color is not sediment alone; the same fog that blankets the swamp hangs suspended in the water itself, so that a jar drawn at noon still glows faintly at its bottom.
Drink it and you see things. The swamp as it was before the queen came, or as it might be after she falls, or as it runs in some other Phirexes where the choices went differently. Some of the visions are beautiful. Most are not. A few have come true.
The Dengar alchemists prize Mud Run water for exactly that and fold it into compounds that can be brewed nowhere else. The queen watches its harvest as she watches every resource that has worth. She cannot lock a river, but she can count who comes to it.
Refugees keep away. The water shows them what they have lost and cannot have again, and that is a cruelty they can do without. One of them does not keep away. A Dengar seer called Wisling drinks Mud Run on purpose, holds the visions like a hand of cards, and has begun telling the camps which are true: the year the fogs will lift, and who will be standing when they do. People are starting to move on what she says. Whether she is reading the future or being fed it is the open question, because the fog answers to Phendexelas, and a prophecy that walks the queen's enemies into the open would be the gentlest weapon she owns.