In Greek mythology, Deino (also Dino; Ancient Greek Δεινώ, "dread") is one of the Graeae, the grey sisters who share a single eye and a single tooth. Apollodorus names her beside Enyo and Pephredo (Pemphredo) as a daughter of the sea-gods Phorcys and Ceto and sister of the Gorgons. Hyginus records the variant Persis for this third sister, noting that others call her Dino. She is best known from the Perseus episode in which the hero steals the sisters' shared eye to learn the way to Medusa.
Adapted from Wikipedia, "Graeae" · CC BY-SA 4.0
I.Family and names
The Graeae are daughters of Phorcys and Ceto and sisters of the Gorgons. Hesiod's Theogony names only two grey sisters — well-clad Pemphredo and saffron-robed Enyo — as fair-cheeked yet grey from birth. Apollodorus expands the trio by adding Deino (Δεινώ).
Hyginus, listing them as Phorcides, pairs Pemphredo and Enyo with Persis and remarks that "for this last others say Dino," preserving the Deino/Dino name as a recognized variant of the third sister.
II.Mythology
The Graeae took the form of old, grey-haired women and shared one eye and one tooth, which they passed among themselves. By stealing the eye while they were exchanging it, Perseus forced them to reveal either the whereabouts of Medusa or the objects needed to approach her, ransoming the eye for the information.
Deino has no separate adventure apart from this shared ordeal; her individuality in the tradition rests on her place in Apollodorus' three-name roll and on the etymological sense of "dread" that attaches to her name.
III.Homonyms
This atlas entry (dino-graea) is the Graia Deino/Dino, sister of Enyo and Pemphredo. She is distinct from any later or unrelated bearers of similar names; the collective node graeae holds the two-name versus three-name dispute for the sisters as a group.