The River Styx: Underworld River and Oath of the Greek Gods

The River Styx is, in Greek mythology, both a river of the underworld and a goddess, the eldest daughter of Oceanus and Tethys. Her name means “the Hateful.” Her real job is not ferrying the dead; it is holding the gods to their word. Because Styx was the first to join Zeus against the Titans, her water became the most binding oath on Olympus, and a god who broke it paid for ten years. The Greeks also located the Styx on earth, as an icy waterfall in Arcadia that was said to kill anyone who drank from it.

A goddess before a river

In Hesiod, Styx is a person first. The Theogony (361) lists her among the three thousand Oceanids and calls her “the most eminent of them all.” She marries the Titan Pallas, son of Crius, and bears four children whose names are forces: Zelos (Rivalry), Nike (Victory), Kratos (Power) and Bia (Force) (383-385; Apollodorus 1.2.4).

This is a political family. Styx’s children are exactly what a king of the gods needs to rule: winning, power and the force to compel. In Aeschylus’s Prometheus Bound, it is Kratos and Bia who drag Prometheus to the rock where he will be chained.

One isolated variant, in Apollodorus (1.3.1), even makes Styx the mother of Persephone by Zeus. It never caught on: the standard tradition gives Persephone to Demeter. The Homeric Hymn to Demeter (423) simply lists Styx among the young goddess’s playmates on the day she is carried off.

First to side with Zeus

Styx earned her place during the Titanomachy. Hesiod tells how Zeus called every immortal to Olympus with a promise (389-403): whoever fought beside him against the Titans would keep their honors, and those Cronus had stripped of honors would receive new ones.

Styx came first, with her children, on the advice of her father Oceanus. Zeus rewarded her twice over: he made her “the great oath of the gods,” and her children would live with him forever, wherever he went. Victory, Power, Force and Rivalry never leave Zeus’s throne again. One story explains two things at once: why Zeus’s rule is so secure, and why an oath on the Styx is absolute.

The oath that binds the gods

Swearing by the Styx is the strongest formula the gods have. In the Iliad (15.36-38), Hera swears to Zeus by Earth, by Heaven, and by “the down-flowing water of the Styx, the greatest and most terrible oath for the blessed gods.” In the Odyssey (5.184-186), Calypso uses the same words to promise Odysseus she is not setting a trap.

Hesiod describes the ritual (782-806). When a god is suspected of lying, Zeus sends Iris far away with a golden jug to fetch the icy water of the Styx, which falls from a high rock. The god swears while pouring it out. If he lies:

• he lies a whole year without breath or voice, never touching nectar or ambrosia, wrapped in an evil stupor;
• then he is barred for nine years from the councils and feasts of the gods;
• only in the tenth year does he take his place again.

The punishment is striking because it falls on immortals. They cannot die, so the Styx inflicts the closest thing to death: no breath, no divine food, no company.

The oath drives plots. Later poets enjoy showing a god trapped by his own word: in Ovid (Metamorphoses 2.44-48), Helios swears by the Stygian marsh to give Phaethon anything he asks, and then cannot refuse him the chariot of the Sun that will kill him.

The palace of Styx

Hesiod also gives Styx a home (775-779). She lives apart from the other gods in a famous palace roofed with great rocks and held up on every side by silver pillars that rise to heaven. Her water is a tenth part of Oceanus (789-792): nine streams wind around the earth and the sea, and the tenth pours from a rock as a bane to the gods.

So the Styx is wired into the river that circles the world. It belongs to the geography of the depths, near the palace of Hades and Tartarus.

The Styx in the map of the underworld

In Homer, the Styx is already an underworld river. In the Odyssey (10.513-514), the Cocytus is “a branch of the water of the Styx” and flows with the Pyriphlegethon into the Acheron. In the Iliad (8.369), Athena recalls that Heracles, sent to fetch the hound of Hades, would never have escaped “the sheer streams of the Styx” without her. The Catalogue of Ships (2.751-755) even makes the Titaressus, a river in Thessaly, a branch of the Styx: its water slides over the Peneus like oil without mixing.

Plato (Phaedo 113b-c) turns the Styx into an underground lake: the fourth great current of the world falls into a wild place “called Stygian,” forms the lake Styx there, and flows on as the Cocytus.

Virgil sets the Roman picture. The Sibyl shows Aeneas “the deep pools of Cocytus and the Stygian marsh, by whose power the gods fear to swear falsely” (Aeneid 6.323-324), and the Styx, “winding nine times,” hems in the dead (6.439). That is where the image of a river encircling the underworld comes from.

Charon’s boat, however, mostly crosses the Acheron in ancient texts. “Ferryman of the Styx” is a modern phrase that owes its success to the Styx’s fame.

The Arcadian Styx: water that kills

The Greeks also showed visitors a Styx on earth, in northern Arcadia near the town of Nonacris. Herodotus (6.74) describes it as a thin stream falling from a rock into a basin ringed by a stone wall. The Spartan king Cleomenes wanted to make the Arcadian leaders swear there: the earthly Styx was believed to carry the same force as the gods’ river.

Pausanias (8.17.6-8.18.6) saw the falls: water dropping from a cliff higher than any he knew, then joining the river Crathis. He reports that it is deadly to people and animals, that it breaks glass, crystal and pottery and eats through metals, and that only a horse’s hoof can hold it. A rumor told by Plutarch (Life of Alexander 77) turned it into a poison: water from Nonacris, carried in a donkey’s hoof, was supposed to have killed Alexander the Great. Plutarch adds that most people thought the story was made up.

The waterfall is identified today with the Mavroneri, the “Black Water,” which drops from the slopes of the Aroania range (Mount Chelmos) in the northern Peloponnese.

Achilles’ heel: a late legend

In Statius’ Achilleid, written in the late first century CE, Thetis dips the young Achilles in the Styx to protect him from weapons. This is the earliest surviving literary account of the bath (1.133-134, 268-270 and 480-481). Thetis wishes the protection were complete. The poem leaves the vulnerable spot unspecified. Fulgentius later specifies that the heel alone stayed out of the water (Mythologies 3.7).

Homer knows nothing of it: the Achilles of the Iliad is the strongest warrior alive, not an invincible body. Older writers tell a different attempt by Thetis, using fire and ambrosia (Apollonius of Rhodes, Argonautica 4.869-879). The arrow of Paris that finds the heel is told in the death of Achilles.

How the ancient sources differ

• Hesiod is the main source: the goddess, her family, her alliance with Zeus, her palace, the ritual and the penalty for perjury.
• Homer knows the oath and the river but not the goddess’s story.
• Herodotus and Pausanias place the Styx in Arcadia and describe its water.
• Plato makes it a lake in the underground river system.
• Virgil makes it the marsh that encloses the dead.
• Statius gives the earliest surviving literary account of Achilles’ bath in the Styx. The story may have circulated before him.

Why the Styx matters in Greek mythology

The Styx connects two worlds we usually keep apart: Olympus and the underworld. The word of Zeus and the gods rests on water from the land of the dead, the only thing that can bind immortals. The myth also explains why Zeus’s power holds: Victory and Force are Styx’s children, won by welcoming her on the first day of the war. And the Styx is a rare mythical place the Greeks could actually visit, at the foot of a cliff in Arcadia.

Further reading

For the full map of the land of the dead, read the page on the Greek underworld. Styx’s family appears on the pages of her father Oceanus, her mother Tethys and her daughter Nike. Her decisive choice of side is told in the Titanomachy. The ferryman Charon and the “Styx or Acheron” question are covered on his page. For the heel legend, see Thetis, Achilles and the death of Achilles.