Unlike Imperial Gold and Celestial Bronze, it can harm both mortals and immortals alike. When seen, it is shown to scare monsters even more than the other two metals. Possibly because the essence is absorbed into the blade, which prevents the monster from going back into Tartarus to reform. It also appears to have a significant effect on ghosts and creatures from the Underworld.
Stygian Iron is mined and forged in the Underworld and cooled in the River Styx, producing a clean indestructible blade. Because it is cooled in the River Styx, it is believed that only deities from the Underworld and their demigod children can use it, but other powerful beings have been known to use Stygian Iron.
One large difference between Celestial Bronze and Stygian Iron is the way they kill monsters. Celestial Bronze (as well as Imperial Gold) destroys the monster's physical form and their essence returns to Tartarus, but Stygian Iron is stated to actually absorb/destroy the monsters essence, which most likely means a Stygian Iron weapon can prevent a monster from reforming. One notable user of Stygian Iron is Nico di Angelo, the son of Hades, in the form of a short black sword. Percy describes Nico's sword as being "black as a nightmare."
The forging process for Stygian Iron is similar to that of Stygian Ice, because both are dipped into the River Styx.
After running away from camp, Nico spent some time in the Underworld and managed to obtain a blade of Stygian Iron. He first used the sword when Percy saw him in a dream. While Percy did not know what the sword was made of, Nico used the blade to keep the shades of the Underworld away from his sacrifice until the spirit he wanted approached. The first mention of Stygian Iron by name is when Geryon captured Nico, and then picked up Nico's sword, careful not to touch the blade. Later, during the Battle of the Labyrinth, Nico uses his sword to channel his power and raise an army of the dead who obey his orders, but in doing so exhausts himself and he nearly faints.
Persephone orders a new Symbol of Power to be made for Hades. The symbol is a sword made of Stygian Iron, inlaid with the Keys of Hades, and if completed, Thalia Grace, Nico, and Percy wonder if it would tip the scales of power between the Big Three. It is later revealed that Hades did not know about the weapon's creation, but swears on the River Styx to never use it against the Olympians.
Hades when rising from the Underworld, drew his sword to attack the forces of Kronos. His sword was a double-edged Stygian Iron blade etched with silver, with one of the Keys of Hades concealed within the sword which means that it could either raise a soul from Tartarus, or send another soul straight to the Underworld.
While Nico is visiting his half-sister Hazel Levesque at Camp Jupiter, Hazel comments that Nico always has his Stygian Iron sword at his side. However, his sword is never used before Nico leaves to find information on the Doors of Death, eventually leading to his capture by Gaea.
While Nico is trapped in the jar, he has his Stygian Iron sword at his side. Later on, the sword is placed somewhere else, in order to lure Hazel Levesque, Leo Valdez, and Frank Zhang into a trap made by Gaea when Hazel tries to find Nico by detecting the metal used to make his sword. It is later returned to Nico after he is rescued, and the emaciated demigod initially leans on in like a crutch.
Nico keeps his fearsome sword, and uses it to slay several Katobleps in Venice, to spar undead warriors from time to time, and and later during the climactic battle at the Necromanteion to fight Gaea's army. While helping the Seven fight Clytius, Nico uses his sword to dissipate and absorb the Giant's dark aura, keeping it from affecting any of his friends again.
Nico takes his sword with him during his journey back to Camp Half-Blood with Reyna and Gleeson Hedge. He successfully uses it against Gaea's undead Roman army in Pompeii, slashes the bowstring on Orion's bow, takes down Octavian's elite guard with it, and subsequently wields the sword during the final battle against Gaea's army in Camp Half-Blood.
Stygian Iron is much more dangerous than Imperial Gold or Celestial Bronze. While still able to harm monsters, demigods, and immortals, it can also harm mortals. It is also different in the way it destroys its targets. While most magical metals turn monsters to dust, Stygian Iron will literally drain the life force of its target until there is nothing left and it is absorbed into the blade. This also makes it dangerous to even those that are already dead, such as ghosts and shades. Stygian Iron also has the added benefit of being able to channel the power of the Underworld. For example, Nico has been shown to use his sword to draw the dead to him in order to attack enemies. He has also shown to be able to open up fissures to the Underworld by plunging his sword into the ground, although this is not likely to have anything to do with the actual blade material.
Known Stygian Iron Items
- Nico's Sword
- Hades' Sword
- Hades' Staff
- Hades' Chariot
- Thanatos' scythe
- Clytius' sword
- Clytius' armor
- Koios' armor
- Krios' armor (Possibly)
- Mimas' armor (Possibly)
- Orion's arrow tips
- Nyx's Chariot
- The Doors of Death's outer frame
- Stygian Iron is one of three magical ores, the others being Imperial Gold and Celestial Bronze. However, in Percy Jackson's Greek Gods, adamantine is also mentioned.
- Imperial Gold is Roman, Celestial Bronze is Greek, and Stygian Iron is from the Underworld. It is then possible that the children of Pluto (as well as Hades) could use this metal since the Underworld exists in both Greek and Roman mythology, though this has yet to be confirmed.
- Only Hades, Thanatos, Orion, Tartarus, Clytius, Nyx, and Nico have been stated to have used Stygian Iron so far, making it's appearance far more rare than Celestial Bronze or Imperial Gold.
- When a monster touches it, its essence will be sucked into the blade. However, it is unknown if the monster will ever reform or if it will just take longer for them to reform in Tartarus.
- As it is not silver, it probably does not harm lycanthropes.
- Like other enchanted metals, Stygian Iron gives off a faint light; in this case the light is dark purple.
- According to Jason Grace in The House of Hades, Stygian Iron seems to "make shadows even gloomier, as if the infernal metal was soaking the light and heat out of the air."