Achlys

Achlys, in the Hesiodic Shield of Heracles, is one of the figures depicted on Heracles' shield, perhaps representing the personification of sorrow. In Homer, achlys is the mist which fogs or blinds mortal eyes. Her Roman counterpart Caligo was said to have been the mother of Chaos. In Nonnus's Dionysiaca, she seems to be a witch.

Homer

In Homer, the word achlys, is frequently used to describe a mist that is "shed" upon a mortal's eyes, often while dying. For example in the Iliad, the hero Sarpedon while grievously wounded:
While in the Odyssey, Eurymachus, one of the suitors of Penelope, hit in the chest by an arrow from Odysseus:

''Shield of Heracles''

In the Shield of Heracles, an archaic Greek literature|Greek] epic poem, that was attributed to Hesiod, Achlys is one of the figures described as being depicted on Heracles' shield, where she is understood as being the personification of sorrow or grief:

Beside them stood Death-Mist, gloomy and dread, pallid, parched, cowering in hunger, thick-kneed; long claws were under her hands. From her nostrils flowed mucus, from her cheeks blood was dripping down onto the ground. She stood there, grinning dreadfully, and much dust, wet with tears, lay upon her shoulders.

''Fabulae''

The Roman counterpart to Achlys seems to have been Caligo. The first-century BC Roman mythographer Hyginus, in the Preface of his Fabulae, has Caligo being the mother of Chaos, and, with Chaos, was the mother of Night, Day, Darkness and Ether, possibly drawing on an otherwise unknown Greek cosmological myth.

''Dionysiaca''

Nonnus, in his Dionysiaca, seems to regard Achlys as a kind of witch. According to Nonnus, Hera—angry with the guardians of the infant Dionysus —"procured from Thessalian Achlys treacherous flowers of the field", which she used to sprinkle a sleeping charm over their heads, then "she distilled poisoned drugs over their hair and smeared a magical ointment over their faces", changing their human shape into that of horned Centaurs.