Stheno and Euryale

Classical summaries root Stheno and Euryale in the older, chthonic/sea monstrous generations. Hesiod and Apollodorus list Phorcys and Ceto as their parents, placing them among sea/chthonic offspring that embody natural and liminal dangers. Some later or variant summaries (e.g., Hyginus as cited in modern summaries) provide alternate genealogical connections to other monstrous lineages; the primary surviving classical tradition emphasizes their descent from Phorcys and Ceto.

In archaic Greek iconography and poetic description the sisters share standard Gorgon features: hair of serpents (Pindar describes "horrible snakey hair"), prominent terrifying heads often shown full‑faced (sometimes with little or no visible neck) on running profile bodies, wings on the back, and serpents associated at their girdles (a Hesiodic shield passage describes serpents hanging from their girdles, licking their tongues). Later visual traditions render their heads smaller relative to bodies, with visible necks and less wild expression.

Primary supernatural power attributed in the classical sources is the petrifying gaze: anyone who looked at the Gorgons could be turned to stone (Hesiod; Apollodorus summaries). Stheno and Euryale are described as immortal in these accounts (in contrast to the mortal Medusa). Literary passages emphasize aggressive pursuit — after Perseus beheaded Medusa the two sisters pursued him in retaliation — and vocal expression, with Euryale specifically noted for a loud, shrill lament or bellowing during the chase (Pindar; Nonnus).