In Greek mythology, the Oneiroi were the sons of Hypnos, the god
of sleep. They were personifications of dreams—black-winged
daemon—and were said to live on the shores of the Ocean in the
far West, in a cavern near the border of Hades. The gods sent
dreams to mortals from one of two gates located there: true
dreams emerged from a gate made of horn, whereas false dreams
threaded their way from a gate fashioned of ivory. They are
described in the Odyssey, Hesiod's Theogony, and Ovid's
Metamorphoses. According to Euripides, their mother was Gaea.The
most powerful of the Oneiroi was Morpheus. His brothers Phobetor
(also known as Icelus) and Phantasos crafted parts of dreams,
while he formed the dream in general. Morpheus shaped human
figures, Phobetor animal, while Phantasos shaped inanimate
objects. Oneiroi in Pop Culture Fates Warning, a progressive
metal band, has a side long epic on their 1988 release No Exit
titled The Ivory Gate of Dreams which touches on this myth.