In Greek mythology, Phobetor ("frightening"), Ikelos, Icelos or Icelus was one of the Oneiroi, the personifications of dreaming. According to Hesiod, Phobetor is the son of Nyx, the primordial goddess of the Night, produced parthenogenetically, or as Cicero claims, with Erebus, the embodiment of Darkness. The Phobetor had the ability to appear in the mortal realm in the guise of various animals and could change their physical forms at will in order to interact with mortals in the waking world. Phobetor was the personification of nightmares and appeared in dreams in the form of animals or monsters. Among the gods he was known by his true name, Icelus (Ikelos "semblance"). Together with his brothers, Phobetor resided in the land of dreams (Demos Oneiroi), a part of the underworld.