Here is Huangquan.
If we are alive, then there is a world of death.
Forget the river and the yellow spring, wash away the color of a lifetime, and then enter the next reincarnation.
The water in Wangchuan has no color, but is deep and bottomless. But if you look carefully, you can see all possible or impossible colors fall into your eyes.
That is the collection of colors from the previous life that faded after crossing the River of Forgetfulness. Souls that are about to move on to the next life, whether they have sins or obsessions, will be cleansed here.
And those who travel to and from the Forgotten River to cleanse the souls of the dead are the underworld extraditers.
Extradition from the Nine Realms, but are they really more transcendent than us...?