IX Graeae

Aged virgins, possessing one eye and one tooth between the three; beings on whom no ray of sun ever looks down, nor moon at night.
Aeschylus, Prometheus Bound, 791-800 CE

Goddesses who were born old and became older as time went on, they were the guardians of the powerful and mysterious Gorgons. Whoever held their sleepless eye was all seeing and ever vigilant.

Image source: Red Figure Ware ca. 425 BCE