Hypnos was one of the many relatively minor and very ancient deities of the Greek pantheon. The similarities in appearance and behaviour between the god of Sleep and Hermes (Latin: Mercury) are so apparent, however, that it is compelling to speculate that the two are linked, or that Hypnos is in some way a particular aspect of Hermes. Hermes, also considered a god of sleep, was one of the major Olympian gods and appeared later than Hypnos, it is probable that as Greek civilisation developed the minor, rural deities were absorbed into the official Olympian pantheon in this way.

Hypnos the Bountiful, as he was known by the ancients, rests in the arms of his mother Nyx (Night). His father is Erebus, the pure darkness of Hades, the Underworld. Hypnos dwells with his twin brother Thanatos, god of Death, in a dark cave by the banks of the river Lethe (Oblivion), at the entrance to Hades. The cave is surrounded by opium poppies and other sleep-inducing herbs.

Hypnos is a gentle and benevolent god who sometimes takes the form of a singing bird, sometimes that of a winged youth or old man. He carries a drinking horn, from which he pours sleep-inducing opium. He is most beloved of the Muses, and his spouse is Pasithea, one of the Charities. Together they have three children, Morpheus, Phobetor, and Phantasus who occupy the dreams of men. Morpheus appears in human form in our dreams, Phobetor as birds and animals, and Phantasus as all the animate objects of our dreams.

Hypnos delivers mortals from pain and mental suffering, with the help of his sons and his brother Oniros (Dream) he colours their sleep with dreams. Hypnos opens two gates, the Gates of Horn and Ivory, through which Oniros comes into the minds of men. Through the Gates of Horn come prophetic dreams, and through the Gates of Ivory come deceptive dreams which mislead.

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