Morpheus ( or ) is the Ancient Greek god of dreams who appears in Ovid's Metamorphoses. Morpheus has the ability to mimic any human form and appear in dreams. His true semblance is that of a winged daemon, an imagery shared with many of his siblings. Robert Burton, in Anatomy of Melancholy, refers to Classical depictions of Morpheus, saying "Philostaratus paints (Morpheus) in a white and black coat, with a horn and ivory box full of dreams, of the same colours, to signify good and bad". In myth, Morpheus was also said to send dreams through one of two gates, one of ivory, and the other of horn. Starting in the medieval period, the name Morpheus began to stand generally for the god of dreams or of sleep.