In Greek mythology, Achlys (Greek language: Ἀχλύς "mist") was, according to some ancient cosmogonies, the eternal Night (perhaps the Mist of Death, which clouded the eyes of the dying), and the first created being which existed even before Chaos. According to Hesiod, she was the personification of misery and sadness and as such she was represented on the shield of Heracles: pale, emaciated, and weeping, with chattering teeth, swollen knees, long nails on her fingers, bloody cheeks, and her shoulders thickly covered with dust. If the former is true, then she may have been numbered amongst the Keres. She is also called Caligine or Caligo.