Similar in some fashion to the Tree of Life, the River of Death is likewise some form of astral entity that flows along the entry layers of the Neutral and Lower evil planes. The River of Death is often depicted as a murky and stagnant flow that winds through the various planes and serving as a means of transport from one to another.

The River of Death originates in the region of the Twilight Lands known as the Wellspring and then works its way through the Gloomrealm, the Netherworld, Infernia and finally terminating in Ethyria. The river is thought to be home to all manner of aquatic fiends and is even said to have the power to strip a mortal being of all their past memories. This ability is often used by the gods of the Lower Planes to deprive new petitioners of any memory of their former lives before spending eternity in the wallow of the Lower Planes.

The River of Death radiates a strong antipathy effect against all creatures of good alignment.

Google Source: For additional ideas, consult the google entry under "Styx."