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For thousands of years, you humans have been throwing in everything as you come across—hopes, dreams, wishes that never came true. Irresponsible waste management, if you ask me.

Charon to Percy Jackson, in The Lightning Thief.

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.


The goddess Styx was born to Oceanus and Tethys or the primal goddess Nyx. She married the god Pallas, son of Krios 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.


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.

According to Percy, the river is very polluted, being filled with pretty much anything you could imagine: broken toys, ripped up diplomas, etc. – the scrapheap of human miseries. The river is filled with lost hopes and dreams, as well as wishes that never came true. The river was claimed to be created by the Titan, Tethys, and was fed by salty springs from the bottom of the ocean.

The River Styx is also where Stygian Iron is cooled to make it indestructible, as well as where Stygian ice is formed. Heroes who bathe in it become invulnerable (only Achilles, Luke Castellan, and Percy Jackson have successfully done this, though). 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.

Percy Jackson and the Olympians

The Lightning Thief

While going into the Underworld to visit Hades, Charon ferries Percy Jackson, Annabeth Chase, and Grover Underwood across. As they sail across it, they see how polluted the river is because of all the unfulfilled dreams that are tossed into it by the dead. Percy threw a bed leg from Procrustes's shop into it while to use it as a fetch stick to tame Cerberus.

The Last Olympian

After Percy Jackson has bathed in the River Styx, Hades chases after him with a group of Skeleton Warriors, after he escaped from his cell in Hades' Palace with the help of Nico di Angelo. Percy summons a tidal wave from the River Styx and due to Percy's newly acquired Curse of Achilles, he overpowers Hades, but before he can get any information about Kronos' plans, Hades disappears. Percy releases the tormented souls of the damned from Hades' robe by throwing it into the River Styx.

The Heroes of Olympus

The House of Hades

The main river of the River Styx does not appear (although all five Underworld rivers are said to flow into Tartarus), but its water flows through Tartarus's heart. While fighting at the Doors of Death, Percy causes Tartarus's arteries to explode, disgorging a geyser of Styx water which disintegrates monsters on contact.

The Trials of Apollo

The Dark Prophecy

I will have my due. You will PAY for your broken promises.

–Styx threatening Apollo

The goddess Styx appears to Apollo in a vision while he is suffering the effects of drinking Lethe and Mnemosyne. Styx threatens Apollo with vengeance for his broken oaths, but ultimately dismisses the vision, annoyed by Apollo's Lethe-induced half-amnesia.

The Trials of Apollo

As Apollo fights Python, they both end up in in the river before they are swept into Tartarus.

Swearing on the River Styx

When you break such an oath... Whatever, just don't do it. There are worse things than death.

Hazel Levesque, The Son of Neptune

The River Styx is also part of a powerful oath that can be made between any groups of people. Breaking an oath on the Styx is extremely unwise for anyone due to the fact that once you swear upon it, the Fates are now watching. Gods who break oaths on the Styx apparently "get off lightly" on the account of being immortal, such as when Zeus and Poseidon broke the oath of having no more demigod children after the end of World War II. It is unknown what would happen if a lesser entity were to break an oath on the Styx, but it is considered unpleasant. According to the myths the books are based on, the consequences for breaking an oath made upon it are supposed to be extreme.


The oath-breaker is supposed to be exiled from the assembly of gods for ten years and be denied nectar or ambrosia during this time. The first year they lie in a coma-like state unable to move in any way. The rest they are denied attending any of the assemblies or festivals of the gods for nine years. The former god Apollo broke a River Styx oath in The Hidden Oracle, In the Burning Maze the River Styx made the punishment by intimidating at Apollo and saying that there will be more deaths during his quest.

Despite this, Hades, Zeus and Poseidon avoided this. Since Zeus is in charge of enforcing oaths there was no one to force him to go into exile. His importance in the council and the fact that he maintains order on Mount Olympus probably had something to do with it as well. This was probably brought about by his great arrogance and general dislike for following his own rules. Poseidon's status and power no doubt protected him as well making exiling him too difficult. Ironically, Hades is the only one of the Big Three who kept his oath of not having more children after World War II. In The Son of Neptune, Percy asks Hazel if, because Death is chained, an oath on the River Styx is still binding and she says it is.

Known Oaths

Achilles' Curse

Main article: Curse of Achilles

Anyone who bathes in the River Styx will be gifted with the strength, power, speed, and near invincibility of Achilles. The only spot where one who has bathed in the River Styx is vulnerable is in their Achilles' Heel, a spot of the bather's choosing which will keep them grounded to the real world and their mortal life after they bathe in the river. If the person doesn't focus on that point while bathing in the river, their soul will be incinerated, washed away in the current. Achilles' ghost appears to anyone who wishes to receive the curse, warning them not to. The ghost claims it will affect them highly, but it shows few signs in Percy.

Bearers of the Curse

There have only been three people to have bathed in the river so far and lived:

  • Achilles - His mother dipped him into the river while holding him by his heel early on in his life when he was only a baby years before the Trojan War. Therefore, his heel is vulnerable. He was killed in the Trojan War by an arrow from Paris that struck him in his heel.
  • Luke Castellan - Luke bathed in the river so that his body could become invincible, giving his body the ability to hold Kronos' spirit. His Achilles spot is under his left armpit, in a place that would be very hard to reach. He possibly envisioned himself and Thalia first meeting and starting a romantic relationship and giving his knife to Annabeth Chase. He stabbed himself in the armpit to destroy Kronos before Kronos could take on his true form and died by his own hand to end the Second Olympian War.
  • Percy Jackson - Nico di Angelo suggested to Percy that he should dip himself in the River Styx so that he could defeat the Titan Lord Kronos in the Battle of Manhattan. Percy was first uncertain about this idea but eventually decided to go through with it. His Achilles' Heel was the small of his back, opposite of the navel. He pictured it like the time when he fell out of the boat and was being pulled out of the water by Annabeth. He later lost the blessing after touching the Little Tiber when entering Camp Jupiter, because it is a Greek blessing and cannot survive in the Roman territory.


  • The River Styx is the only body of water that Percy Jackson cannot breathe in or control.
  • Like the rest of the Underworld rivers, the goddess Styx is an immortal nymph, a daughter of Oceanus, but does not take an actual form until Apollo's vision in The Dark Prophecy, where she appears as a woman with black hair, black eyes, and dark makeup, wearing a smoke-like dress.
  • In The Demigod Diaries, Leo Valdez mentions that part of the fuel for the Argo II is water from the River Styx.
  • A promise on the River Styx can apparently be broken if another promise is made on the Styx that cancels it out. For example, the Pact of the Big Three was dissolved when Percy made the gods swear on the River Styx that the pact be broken, as it didn't work anyway.
  • Frank Zhang tried to make the Laistrygonians swear on the River Styx to spare Percy Jackson, Hazel Levesque, and Grandma Zhang if he surrendered to them, but it did not work.
  • Swearing on the River Styx is similar to swearing on one’s Troth in Norse mythology.
Underworld: DOA Recording Studios | Doors of Death | Door of Orpheus | Elysium | Erebos | Fields of Asphodel | Fields of Punishment | Hades' Palace | Isles of the Blest | Judgment Pavilion | Persephone's Garden
Rivers: Cocytus | Phlegethon | Styx | Lethe | Acheron
Tartarus: Mansion of Night | Hermes' Shrine | Chaos