Stygian is an adjective that has come to mean infernal and hellish or gloomy and dark. Those are its more metaphorical meanings; it originally meant pertaining to the River Styx. Styx is Greek for "hateful", but the River Styx is often called "The River of Unbreakable Oath" for the Olympian gods would swear binding oaths on its shores. Styx is one of 5 rivers flowing through the Underworld and the Styx is on the border between Earth and the Underworld. It circles the Underworld 9 times and converges with most of the other Underworld rivers at the center of it, creating a marshy delta. Drinking the water from the River Styx would make anyone, even a god, lose their voice for 9 years. Being submersed in the Styx could also provide invulnerability to mortals, like Achilles, who was invulnerab