Five Rivers of the Underworld served as a physical barrier between the Underworld and the mortal realm. Their presence made sure no one could enter or escape unharmed. There were a number rivers in the Underworld, and each served a purpose.
Acheron was the river of lamentation. Cocytus was the river of woe. Lethe was the river of forgetfulness. Phlegethon was the river of fire. Styx was the river of unbreakable oath, by which the gods swore. It was also the river of hate.
The Styx is probably the river most often mentioned in mythology. Like most river deities, the Styx was an offspring of Oceanus and Tethys that flowed nine times around the borders of Hades. Its waters were not only fatal to the living, but it also broke vessels that tried to contain it and corroded all materials except the hooves of horses. Those who wished to enter the underworld had to be ferried across the Styx by Charon. It was also the river in which Thetis dipped her son Achilles in order to make him invulnerable to any wound.
The river Lethe was also considered important because, since many cultures believed in the transmigration of souls and reincarnation, the souls going back had to drink from Lethe to forget all their former lives and the Underworld.
Jingle Bells.. Batman smells.. Robin layed an egg.. the Batmobile, lost its wheel.. and the Joker got away.. :D
