|“||You cannot kill me! I am the pit itself. You might as well try to kill the Earth. Gaea and I - we are eternal. We own you, flesh and spirit!||”|
Tartarus is the father of Typhon and the giants, of whom Gaia is the mother. The father of Tartarus is Chaos. He is the "prison guard" of Tartarus, the darkest pit in the Underworld where monsters go to reform once they are slain. Tartarus is also the place where Uranus threw, in chains, the Elder Cyclopes and the Hekatonkhieres, and the place where most of the Titans were chained after the First Titan War. He is one of the Protogenoi.
Tartarus takes on a physical form, remarking on how wise his consort Gaia was to consider doing so while she was awakening. Annabeth Chase notes that the only reason she, Percy Jackson, and Bob were still alive was because Tartarus was too busy marveling at his mortal form. She realizes that protogenoi like Tartarus are unlike their descendants to the point that not even a Titan could stand alone against Tartarus. To her dismay, she notes that this was what it would be like if Gaea were to awake fully. Feeling hopeless, Annabeth and Percy resign to fighting to the death against Tartarus. They are saved by the arrival of Tartarus' own son, the giant Damasen. He and Iapetus/Bob sacrifice themselves to allow Percy and Annabeth to escape through the Doors of Death to the mortal side in the House of Hades in Epirus.
After hearing a voice calling for help from the depths of Tartarus, Nico di Angelo suspects that it could be Iapetus, suggesting that he had survived his encounter with Tartarus at the Doors of Death.
|“||Be honored, little demigods. Even the Olympians were never worthy of my personal attention. But you will be destroyed by Tartarus himself!||”|
Consistent with the primordial responsible for the most terrible infernal abyss, Tartarus is a totally evil, somber, sadistic, and terrifying entity that, like its domains, brings only despair and fear to all below it through the most exquisite forms of cruelty. He showed himself to be a highly arrogant god with an immense disdain and contempt for humans and even the titans, whom he openly described as "lesser beings" after easily destroying them. However, Tartarus is honest and admits when someone forces him to take direct action.
Like some primordial ones, Tartarus does not like to manifest his physical form, since that prevents him from being everywhere in his domains, but at the same time, he even claimed to have a taste for having a physical form and also showed delight in inciting terror in its victims. Like Gaea, he also takes great pride in his Gigantes children (except for Damasen).
However, like some of his brothers, he also proved to be generally an impartial entity, to the point of being completely devoid of feelings and ideals as he remained neutral and almost ambivalent of the constant wars that were waged between the gods against the titans, and even claiming that he does not usually interfere. But at the same time, Tartarus's impartiality has limits, since he joined Gaea more than once to overthrow the Olympians and, millennia later, dealt personally with Percy and Annabeth.
Tartarus is monstrous in his physical form, standing at immense height, his purple glistening flesh rippling with muscle. His fingers are tipped with razor-sharp black talons. However, his most terrifying and distinguishing feature is his face- in place of a normal face is a swirling whirlpool and inward spiral of darkness, and his voice sounds like it is being drawn back inward rather than projecting outward. Tartarus' black Stygian iron boots are each the size of a coffin, and his hands are as large as crane scoops. His breastplate has faces of gorgons, monsters, cyclopes and dragons all pressing against his armor as if trying to escape. According to Percy, Tartarus is so massive, and radiates such pure malevolence, that Percy wanted to crawl away and hide as soon as he saw him, and even dropped his sword in terror. Tartarus' laugh sounded like a mountain "cracking in half". According to Annabeth, everything around Tartarus seemed to be drawn to him.
As the Protogenos of the Primordial Abyss, Tartarus proved to be one of the most powerful and terrible entities of the series and infinitely powerful while in its domains. He possibly is the most powerful Protogenos though Gaea and Ouranos rival him with the sole exception of Chaos as he can suck in Titans whereas Gaea and Ouranos could not. Proof of his terrifying power was that even the Titans could not threaten him since he easily defeated Krios, Hyperion, and possibly Iapetus without much difficulty. Even after the arrival of Damasen, the maximum that did was to distract so that Percy and Annabeth escaped since there would be no way to defeat him in his home domain. And even so, he overpowered all his opponents (which included a Titan and a Giant) within moments even though he was only using a small manifestation of his power. According to Annabeth, if Tartarus wanted to, he could kill them all with a single thought, if it were not his desire to experience the pleasure of killing his victims one at a time as he rarely assumes physical forms.
- Supreme Power: As the Protogenos of the Abyss, Tartarus holds immense levels of power and was so powerful that Annabeth Chase stated that Tartarus could kill her and Percy with a single thought if he wanted to. His mere presence was more than enough to scare Percy into submission. In fact, not even the Titans pose any challenge to Tartarus and he himself was able to easily defeat Krios and Hyperion though he caught them by surprise. It took Iapetus, Damasen, Small Bob, and the Drakon just to hold him off long enough for Percy and Annabeth to escape, and even combined they apparently were defeated, even though he was only using a small manifestation of his power.
- Godly Strength: Tartarus has incredible physical strength, far surpassing that of even a giant or a Titan, and was easily able to overwhelm Iapetus and destroy his Spear. He was even able to hold his own against and apparently ultimately defeat Damasen, Iapetus, Small Bob, and the Drakon all at once while in a physical from of limited power, though the Titan and giant were both at a fraction of their full power. Not even his own children pose any challenge to him as he easily defeated them. They only hold him off all at once though they were all at a fraction of their full power and even combined they were defeated.
- Dark Gravity: Tartarus also has something like a dark gravitational field around him, which pulls everything in his close proximity into his terrifying whirlpool of a face.
- Essence Absorption: Tartarus has the ability to suck beings into the swirling whirlpool of darkness on his face, which he did to the immortal essence of Hyperion and Krios. In that sense, Tartarus can "kill" gods, Titans, and giants by absorbing their immortal essence into his armor for very long periods of time, though it is unknown to what extent he can use this power.
- Monster Lordship: As the Protogenos of the Abyss, Tartarus has absolute control and divine authority over monsters.
- Umbrakinesis: As the Protogenos of the Abyss and the Pit of Evil, he has absolute control and divine authority over darkness, although not so much as Nyx and Erebos.
- Darkness Generation: He can shoot solid bolts of darkness, and surround enemies in pitch-black clouds of lightless space.
- Darkness Shields: He can solidify shadows into virtually impenetrable shields.
- Invisibility: He can use shadows to cover himself in darkness to become invisible.
- Shadow Travel: Using shadows, he is able to travel anywhere he wants at incredible speeds.
- Telumkinesis: Tartarus can likely summon and control weapons that cause pain and suffering.
- Power Suppression: Just by being in his domain, Annabeth's innate capacity to heal slowed to a near halt forcing her to drink from the River of Fire.
- Tartarus, along with Percy and Annabeth, appears on the UK and the Dutch cover of The House of Hades.
- Tartarus, like the location that shares his name and that he is, is able to hold monsters within himself. He was even able to hold Titans, such as Krios and Hyperion though it is unknown for how long - possibly forever as Percy said in The House of Hades.
- He is the step-father of the six Elder Titans.
- Like most protogenoi, Tartarus's power lies not in combat but in his manipulation of the physical pit of Tartarus. It can be assumed that he was only able to easily defeat Krios and Hyperion, two Titans at a fraction of their full power because he caught them by surprise and had their allegiance, as it took him much longer to defeat (if he did) a Titan and a giant of similar power.
- Although Tartarus tells Percy and Annabeth that not even the Olympians deserved his attention, this is not entirely correct, as he has helped Gaea twice to try to destroy the Olympians, if only indirectly.