The River of Wights runs down out of the northwestern highlands of the Crimson Coast, feeds the Pools of Tragedy on its way, and empties south into the Void. It earns its name in the dark. The upper reaches are genuinely haunted, bodies dropped into the water do not always stay down, and the fishers along its lower stretches learn early which bends to leave alone after sunset.
Everywhere else, raising the dead takes a caster. It takes a necromancer paying in Deoric and in life to hold a shadow knotted to the corpse it should have left. Here it takes nothing. The current of the First Dark, which drains released shadows down to Malstaris, runs slow over this riverbed, so the shadows of the violently dead are not pulled away. They linger in the water and catch on whatever is near. Where that is a corpse, the shadow knots back into it and the body rises on its own. The dead that rise this way are wights: they keep the cunning and the spite of the people they were, without keeping the mind. No one made them. No one owns them, and no one can call them off.
What feeds the river is the killing upstream. This is the southwestern country of an old Winter Elf kingdom that broke apart in civil war, and the river holds that war's dead. The blood runs back to the murder of King Istor XXVI and the fight over his throne between his daughter Lamenrae and his uncle Taoinor, the quarrel that split the realm into Klevnaf and Istora. Each half blames the other for the king's death. The water keeps no opinion on the matter. It keeps the dead.
Two stretches you can fish. The middle reach by the falls, and the mouth where it meets the Void, and even the mouth I'd not work past dusk. Everything between, you leave to them. My grandfather lost a brother pulling a net up there. Brought up more than the net. — a fisher of the lower River of Wights
By the time the river reaches the Pools of Tragedy its water already carries the residue of all that dying, and the pools hold it the way a still basin holds silt. Downstream of the pools the haunting thins but never fully clears, which is why the lower river is fished at all, and why it is fished carefully.