Hypnos
In Greek mythology, Hypnos (Ancient Greek: Ὕπνος, "sleep") was the personification of sleep; the Roman equivalent was known as Somnus. His twin was Thánatos (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. His dwelling has no door or gate so that he might not be awakened by the creaking of hinges.
Read more about Hypnos.