River Styx

The River Styx is a sacred river that separates the land of the living from the realm of the dead, one of five which run through the Underworld. Oaths made by this river brings something 'worse than death' to the oath bearer if not fulfilled. If anyone bathes in the Styx and survives, that person will bear the Curse of Achilles and become invulnerable to most physical attacks, excluding a small spot on their body that if struck will instantly kill them.
==History==
The goddess Styx was born to Oceanus and Tethys or the primal goddess Nyx. She married the god Pallas, son of Crius and Eurybia, and has four children with him: Zelos, Nike, Kratos and Bia. During the First Titanomachy, Styx swore loyalty to Zeus, being the first to do so, and to honor her, Zeus proclaimed that the gods would swear oaths by her and that her children would live with him on Mount Olympus.
==Description==
The river was a sacred place to both gods and men. It circles the Underworld nine times, eventually converging on a great marsh at the center of the Underworld with the rivers Phlegethon, Acheron, and Cocytus (though there is a fifth river: Lethe). The Styx is a branch of the Acheron, together with Cocytus, and acts as a moat for Erebos.
Styx was also a goddess - similar to the rivers Phlegethon, Acheron, and Lethe being associated with deities - and a daughter of Oceanus and Tethys. She was the wife of Pallas and bore him Zeus' four winged enforcers: Kratos, Nike, Zelus, and Bia (and sometimes Eros). Styx supported Zeus in the Titanomachy, being the first to aid Zeus in the First Titan War against Kronos and his Titan Army. For this, her name was honored by being used in binding oaths.