Tartarus is the most horrifying, darkest, and deepest area of Hades' realm, known as the Underworld, where the gods imprison their enemies. Tartarus is also the primordial Greek god of Nothingness, the third one to manifest in yawning void of Chaos. When a monster is slain, it is sent to Tartarus until they reform, for a time ranging from days to sometimes centuries. Only immortal enemies are sent here, the mortals are sent to the Fields of Punishment.
While Erebus is the main realm of the dead in ancient Greek mythology, Tartarus also contains a number of villains from Greek history. In early stories, it is primarily the prison for defeated enemies. The first beings to be jailed there, however, were the Cyclopes and the Hekatonkheires. The Titans were condemned to Tartarus after their battle with the Olympians. The Hekatonkheires, after the Titanomachy, became the guards of Tartarus with the Titans imprisoned. Kronos is known for being held there. Later Greek Mythologies depicted Tartarus where the dead souls who were wicked in their lives were also placed. But in this series, the souls of the wicked, including those listed in Tartarus in the myths like Tantalus and Sisyphus are sent to and imprisoned within the Fields of Punishment.
According to the Greek poet Hesiod, a bronze anvil falling from heaven would take nine days and nights to reach earth, and an object would take the same amount of time to fall from earth into Tartarus. Tartarus is described as a dark, gloomy pit, surrounded by a wall of bronze and beyond that a three-fold layer of night. It is one of the primordial objects that sprung from Chaos, along with Gaea, though some believe it was a son of Aether and Chaos, whilst Orphic sources claim Tartarus to be the unbounded first-existing entity. Tartarus is also the father of Typhon and the Giants, of whom Gaea is the mother.
Although it is frequently mentioned within the series, Percy Jackson only visits the entrance of Tartarus once. While the group goes to the Underworld to confront Hades, the cursed shoes given by Luke Castellan drag Grover Underwood to the entrance. When Percy gets to the entrance, Kronos speaks to him, and he realizes that the dreams he had been having before were from Tartarus.
In the Labyrinth, there is a bottomless pit that is connected directly to Tartarus. Percy does not dare to explore this deep pit.
After being rescued from the giants Otis and Ephialtes, Nico di Angelo reveals that he discovered the location of the Doors of Death. The Underworld side of the doors is located in Tartarus. Nico adds that Gaea's minions are strongest in Tartarus, and despite being the son of Hades, he was overwhelmed and captured immediately.
Meanwhile, Arachne tells Annabeth Chase that the power of the Athena Parthenos draws monsters from Tartarus; the floor of her chamber is held together only by fragile tile and spider webs, and beneath is a pit which leads directly to Tartarus. Shortly after, Arachne drags Annabeth into the pit. Percy grabs her by the hand, but does not have the strength to pull her or himself back out. Charging Nico to lead his crewmates of the Argo II to the earth side of the Doors of Death and refusing to leave Annabeth, Percy lets go, and he and Annabeth tumble into Tartarus.
- Kronos (formerly)
- Erebus (by some accounts)
- Nyx (leaves during the night and comes back during the day)
- Hemera (leaves during the night and comes back during the day)
- Arke (messenger of the Titans thrown down after the first Olympian war)
- Chimera (According to his collar in The Lightning Thief)
- Titans (some were known to have been released, others may still be prisoners)
- The Gigantes (but now are rising)
- Numerous monsters that were slayed by heroes.
- Percy Jackson (Fell in with Annabeth Chase in The Mark of Athena)
- Annabeth Chase (Fell in with Percy Jackson in The Mark of Athena)
- It is said that Tartarus is darker than Erebus, which is ironic given that Erebus is the embodiment of darkness and Tartarus' brother (being himself a Protogenos).
- Typhon is currently imprisoned in Tartarus, but the myth says that Tartarus is Typhon's father by Gaea. This fact ironically means that Tartarus is the jailer of his own son, though probably not by choice.
- Tartarus is once misspelled as "Tatarus in" The Lost Hero.
- Between both series, three entrances to Tartarus have been shown. One in the Underworld, one in the Labyrinth, and one underneath Rome.
- Nico di Angelo is the first demigod to survive Tartarus (although Gaea's forces captured him easily and sent him to the mortal world).
- Tartarus is the only known figure to be both a place and a protogenoi.
- ↑ The Lost Hero, Chapter 50