In Greek mythology, Achlys (Greek language: Template:Polytonic "mist") was, according to some ancient cosmogonies, the eternal Night (perhaps the Mist of Death, which clouded the eyes of the dying). According to Hesiod, she was the personification of misery and sadness, a daughter of Nyx (Night) 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.
- Scut. Here. 264, &c.