Hypnos in Wikipedia
In Greek mythology, Hypnos (Ὕπνος, "sleep") was the
personification of sleep; the Roman equivalent was known as
Somnus. His twin was Thßnatos (Θάνατος, "death"); their mother
was the primordial goddess Nyx (Νύξ, "night"). His palace was
a dark cave where the sun never shines. At the entrance were a
number of poppies and other hypnogogic plants.
Hypnos's three sons or brothers represented things that occur
in dreams (the Oneiroi). Morpheus, Phobetor and Phantasos
appear in the dreams of kings. According to one story, Hypnos
lived in a cave underneath a Greek island; through this cave
flowed Lethe, the river of forgetfulness...