Styx (stĭks) [key], in Greek mythology, river of Hades that the souls of the dead had to cross on their journey from the realm of the living. It was a sacred river, and by its name even the gods took their most solemn oaths. The river was personified as a nymph, daughter of Oceanus and Tethys and mother of Nike. There is a river Styx in the N Peloponnesus (in ancient Arcadia).
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