The Greeks...

Hades (also called Pluto in Roman Mythology) was the god of the Underworld. Within the Underworld flowed several subterranean rivers: Acheron, the Cocytus, the Phlegethon, the Lethe and the Styx. The Acheron was a main river with its tributaries, the Cocytus, swelled by the Phlegethon. the Lethe and the Styx. To cross Acheron (and hence the Styx) it was necessary to apply to old Charon, the official ferryman of the Underworld. The cost of the journey across the river was an obulus (one-sixth of a drachma, about a penny, so everyone could afford the trip). The Greeks therefore always put an obulus on the tongue of the deceased before burial. Guarding the Underworld was Cerberus, the monster watchdog with fifty heads (sometimes also three heads). He was born of the giant Typhoeus and the goddess Echidna (echidna is one of the few mammals which does not have REM sleep). Those who drank the waters of the Lethe forgot the past, and Lethe flowed to the extremity of the Elysian fields where they would live in peace and harmony, and also to the end of Tartarus, where the bad were punished (i.e. Christian Hell).

Hades had several auxiliaries including Thanatos (Death), who supplied Hades with his subjects. Thanatos was usually represented as a winged spirit and completely resembled his brother Hypnos (Sleep) who lived with him in the Underworld. Hypnos put men to sleep by touching them with his wand, or fanning them with his large wings.

The son of Hypnos was Morpheus, God of dreams while Asclepius, the God of Health and Healing and son of Apollo, learned the science of medicine from the centaur, Chiron, but was later killed by Zeus by raising the dead Hippolytus to life. His daughter was Hygeia, and her sister was Panacea. All these deities were worshipped by the Greeks.

Hypnos was the God of Sleep in Greek mythology. He is usually depicted in myth and literature as a gentle, benevolence God who brings the restorative gift of sleep to mortals and Gods alike.

The Ancient Greek poet Hesiod claims that Hypnos mother was Nyx (the Goddess of night). According to Hesiod Hypnos did not have a father, however he did have a brother, Thanatos (the God of death). Hypnos and Thanatos were usually portrayed together, the pair cooperated on a number of occasions together. In Homer's Iliad, Hypnos and Thanatos gently carried away from the battlefield the body of Sarpedon, who was killed in battle.

Hypnos also acted alone, Homer describes a scene involving Hypnos, Hera and Zeus. Hera wants to distract her husband Zeus from the events that are taking place and she asks Hypnos to cast a spell on Zeus. Hypnos is reluctant, as Zeus is the ruler of Olympus. However he agrees when he is offered an irresistible bride (Pasithea) as a bribe.

Hypnos is the father of Morpheus (the God of Dreams). In Roman mythology Hypnos was known as Somnus.