Styx

Styx is the eldest daughter of Oceanus and Tethys, the goddess of the underworld river by whose water even the gods swear their gravest oath. Hesiod says she earned that honour by being the first to side with Zeus against the Titans.

In Hesiod's Theogony she marries the Titan Pallas and bears him Zelus (Rivalry), Nike (Victory), Kratos (Power) and Bia (Force). When Zeus calls the immortals to Olympus and promises honours to all who fight the Titans with him, Styx, on her father's advice, comes first, bringing her children. Zeus makes her the great oath of the gods and keeps her children always at his side. She lives apart from the other gods, in a lofty house roofed with rock and held up by silver columns; her water, a tenth part of the stream of Oceanus, falls icy cold from a high cliff, and when a god must swear, Zeus sends Iris to fetch it in a golden jug.

Hesiod also spells out the penalty. A god who swears falsely by that water lies breathless for a whole year, without nectar or ambrosia, sunk in a heavy stupor; then for nine more years he is shut out from the councils and feasts of the gods, and only in the tenth may he return. In Homer, Hera swears by the Styx to Hypnos and to Zeus, and Calypso to Odysseus. Apollodorus even makes Persephone the daughter of Zeus and Styx.

Her name comes from a Greek verb meaning to loathe. Roman poets turned the Styx into the marsh that the dead must cross in Charon's boat: Virgil has it wind nine times around the underworld, and Statius' Achilleid tells how Thetis dipped the infant Achilles in its water. The Greeks also placed it on earth, in a waterfall near Nonacris in Arcadia; Pausanias reports that its water was deadly and broke every vessel except one made of a horse's hoof. Dante makes it the swamp of the wrathful in Hell.