For a god to swear by the Styx is to reaffirm the absolute permanence of its waters, as indicated by the epithet aphthito- ‘imperishable’ in Hesiod Theogony 389, 397, 805. See the comment on I.02.046; also the comment on Homeric Hymn to Demeter 259, where Demeter swears by the Styx that she would have made the child Demophon athanatos ‘immortal’ and agērōs, 260, if the mother of this child had not spoiled what the goddess intended.