Immortal

Immortals are beings who are immune to death through any conventional means, which is what separates them from regular mortals. There have been instances where a mortal or demigod has been gifted with immortality by the gods, usually as either a reward for great heroism (e.g. to Heracles and Percy) or so that they may be united in marriage with a god (such as in the cases of Psyche and Eros also Dionysus and Ariadne).
== Characteristics ==
Immortals are immune to death in any form. They don't age, nor can they die from poison or disease. They are immune to all weapons that mortals use, as they are not forged from magical metals such as Celestial Bronze, Stygian iron, Imperial Gold, or Bone Steel. If their bodies are somehow harmed or destroyed they will eventually reform, though the length of this process can vary from days to centuries. Almost all immortals are typically hidden from human view by the Mist and have supernatural abilities far surpassing those of normal mortals. They tend to show some predictability: most tend to be very prideful and arrogant, not willing to accept help from lesser beings even to the point of fading. Immortals tend to follow "patterns", as the Second Titan War and the Giant War are both just history repeating itself, though with some variations.
=== Limitations ===
==== Greco-Roman Gods ====
The immortality of the Greco-Roman gods, Titans and monsters has its limits:
* Void of Chaos: Chaos is believed to be one of the few things able to truly kill an immortal (possibly by permanently absorbing their divine essence with it being impossible for it to ever escape), as Zeus held Hera over Chaos after her rebellion, threatening to drop her into the void.
* Fading: Immortals can "fade" away into nothingness, ceasing to be, should they lose the will to live or be forgotten or their realms are weakened enough, which has happened to several immortal beings, such as Helios, Pan and Selene. Harpocrates was able to will himself into fading from existence, taking the long-lived Cumaean Sibyl with him who also desired a final end.
* Scattering: If the body of an immortal being is damaged enough, they may be weakened into a state where they can no longer reform for many centuries, at the very least, even to the point of not being able to gather a complete consciousness. Ouranos, Kronos, and Gaea are the only known immortals to have succumbed to this fate. The extremely few weapons powerful enough to destroy the bodies of immortals in such a way are Kronos' scythe, Zeus' master bolt, and Poseidon's trident.
* Tartarus Essence Absorption: The infernal Lord of the Pit 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 technically "kill" gods, Titans, and giants by absorbing their immortal essence into his armor for very lengthy periods of time.
* Seat of Power Destruction: Immortals are always severely weakened when their thrones (representing their seats of power) are destroyed. Zeus ultimately used this method to prevail against the Titans at the end of the First Titanomachy and Kronos was almost successful in using the same method against the Olympians at the end of the Second Titanomachy. The Giant King Porphyrion theorized that a similar yet even more severe weakening of the Olympians could be achieved by destroying the Athenian Parthenon, as it was located at the gods' "roots" as the original Mount Olympus was located in Greece.
* Secure Imprisonment: Immortals can be sealed away in extremely secure prisons, such as the bronze fortress in the depths of Tartarus, which was the fate of most of the Titans. Atlas was notably imprisoned on Mount Othrys, unable to leave while the incredible weight of his celestial burden rested on his shoulders.
* Magic: According to Apollo, magic to destroy a god is entirely possible if they are powerful enough, provided their victims are weak enough to be overcome. Magic also can drain a god’s power and immortality and granting it to someone else.
* Immortality Revocation: Zeus has shown the ability to revoke the immortality of his fellow gods and turn them into mortals, having done this three times to Apollo. However, in Apollo's case, his powers appeared to be bound more than stripped as he still had bursts of godly power. In addition, when the Titaness Calypso left her prison island of Ogygia, she lost all of her powers, including her immortality, leaving Calypso as an ordinary mortal girl. However, with the help of a jump start from Britomartis and training, Calypso was able to regain her ability to use magic.
==== Norse Gods ====
Norse Gods are perhaps the most vulnerable of all. While being beings of great power and are seemingly unable to die from old age, they are able to be killed quite easily by other gods, monsters, and even mortals (Kvasir was killed by dwarves). Norse deities enter the underworld when they die, and can be returned to the land of the living (as is the case for Baldr and Kvasir). Almost all the Aesir are destined to permanently die during Ragnarok.
== Heroes ==
In both ancient mythology and in the series, heroes who have been distinguished for remarkable talent have been given the choice to become immortal. However, it is possible for the chosen hero to reject the gift. In order to create an immortal, Gods must give up a piece of their own immortality, their powers. They cannot create a deity stronger then they are, only weaker as power trickles down not up. The more power they give, the weaker they become.
=== Dionysus ===
Dionysus was once a demigod son of Zeus. He was made immortal for helping the gods greatly in The First Giant War.
=== Heracles ===
Heracles was the son of Zeus. He was a great hero known for the Twelve Labours Of Heracles and the First Giant War. The gods recognized that and he was made immortal upon his death.
== Einherjar ==
Odin's einherjar cannot be killed while they remain within Valhalla and will simply keep resurrecting from mortal wounds every time until Ragnarök.
They do not, however, have this ability outside of the hotel while they visit any of the Nine Worlds, where they are rendered completely mortal.
== Hunters of Artemis ==
The Hunters of Artemis are Artemis's loyal maidens and sisters-in-arms. They have sworn an oath to her, vowing to remain a virgin forever. With this, they gain eternal life and youth by her side. They cannot die from disease or age, but they can die in battle. If they break their vow to Artemis by falling in love, they are once again rendered mortal. Bianca Di Angelo said she felt different after taking her oath.
Thalia Grace claimed she must join the Hunt as she never felt peace since Half-Blood Hill. This might be because time moved slower when she was a pine tree, seemed to speed up as a human, and slowed down again when she became immortal again.
=== Hemithea and Parthenos ===
Hemithea and Parthenos were turned into minor goddesses by Apollo. They later joined the hunt, however, their immortality was not as a result of that. Hemithea later gave up her immortality, instead choosing to grow old with Josephine.
== Gigantes ==
The giant children of Gaea and Tartarus are immortal and will heal from mortal wounds at incredible speeds, unless killed by the combined efforts of a demigod and a Greco-Roman god. It is also possible for a demigod and a Titan, as shown when the Titaness Hecate helped kill her bane Clytius.
==== Alcyoneus ====
The only one of the giants with a different form of immortality is Alcyoneus, as long as he remains within his native territory (Alaska in The Son of Neptune), and will regenerate after mortal wounds at incredible rates, with or without godly assistance. However, when taken out of that territory, the giant can be killed by any means.
== Monsters ==
While monsters can age, most monsters can't die as mortals do and will eventually come back. Whenever a monster is killed, their essence will return to Tartarus and reform, allowing them to return to the mortal world. This is true for almost all monsters, giving them some form of immortality as they can never truly die. However, the time it takes to reform can take anywhere from a few days to a few centuries to a few millennia.
Like the gods, monsters can fade from existence if they lost their will to live and if people don't believe in them, like in the case of Pan, they will fade from existence. In the case of Briares' brothers, they had faded because no one believed in them, but Percy suggested that they also stopped believing in themselves. The same can happen to monsters if not enough people remember them, but Gaea managed to find a way to reverse this somehow, as she brought back Medusa's sisters, who Medusa had claimed faded in The Lightning Thief.
== Daimons ==
Nymphs and satyrs can be considered immortal in the sense that they will never die of age. They are, however, subject to death by other means.
=== Satyrs ===
Satyrs will be reincarnated into something in nature if they die, such as a laurel.
=== Nymphs ===
Nymphs, such as Dryads and water nymphs, can live forever, as long as the thing their life-force is tied to isn't destroyed (plant life and bodies of water respectively). If their life force is destroyed, they will die as well.
== Germani ==
The Germani resurrected by Nero were granted a form of immortality similar to that of a monster's. As a result, when they are killed, the Germani disintegrate into ash. A consequence of this appears to be that the Germani are left somewhat more vulnerable with wounds that wouldn't normally kill a person, such as an arrow to the crotch, killing them instead of just being painful.
The Germani's immortality is linked to Nero's as a god. After Apollo breaks Nero's fasces and kills the god-emperor, the Germani lose their immortality and become mortal men again. Apollo notes that some of the surviving Germani are sporting wounds that would've normally turned them to ash, but which are no longer fatal to them since they are back to just being regular humans again.
== Trivia ==
* When Grover Underwood explains to Percy about what it means to be immortal in The Lightning Thief, Percy thinks it sounded like a pretty good deal. However, when he was offered to become immortal in The Last Olympian, he refused in favor of another gift.
* Mars seems to believe that mortals have it easy because they can die and said something along the lines of it in The Son of Neptune while talking to Frank Zhang.