River Styx/Charon
Charon was the son of Nyx, goddess of night, and Erebus, god of darkness. His purpose in the Underworld was to take the dead across the rivers to whatever area of the Underworld they were destined for, Tartarus for the bad, Elysian Fields for the good. Charon was usually depicted as a human-like man, but sometimes was depicted as a demon or monster. The River Styx, where Charon Ferries souls was the main river in the Underworld, but it was also the embodiment of Styx, goddess of oaths, who had sided with Zeus during the battle with the Titans. Because of the goddess' loyalty, the River Styx became an important feature in the life of the deities, and gods and goddesses would swear oaths on it. This relation of river and ferryman is great allegory for Loyalty in life, and Death in life that we must all pass through.