Acheron

This article concerns the Greek river. For other uses, see Acheron (disambiguation). The Acheron is a river located in the Epirus region of northwest Greece. Acheron translates as the "river of woe" and it was believed to be a branch of the underworld river Styx over which in ancient Greek mythology Charon ferried the newly dead souls across into Hades.
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(n.)
A river in the Nether World or infernal regions; also, the infernal regions themselves. By some of the English poets it was supposed to be a flaming lake or gulf.
  

[Greek] The name of one of the five rivers (occasionally also regarded as a lake) that flow through the realm of Hades. The name means "river of woe", and is often metaphorically used for Hades itself. Here the shades are ferried across by Charon. (Virgil VI, 107).

Acheron (Greek) [probably from achos pain, distress; Etruse Acceruns] The River of Woe, one of five rivers surrounding Hades. The others were Cocytus (river of wailing), Styx (the hateful), Pyriphlegethon (the fiery), and Lethe (forgetfulness).
In later traditions, a son of the sun (Helios) and Demeter who supplied the titans with drink when they were fighting against Zeus, and was therefore transformed into a river of the underworld. These rivers have reference to the circulations of the universe, and in this connection the ancient Greeks and Romans had certain mystical rites relating to the "deification" of souls after death and their passage into other spheres.