Embi: Mmmmm—I am not sure, but 130 in the least [...] When I was young and rash, I made a sacred vow to see the world before I died. Frankly, I didn't know how big it was at the time.
Agatha Clay: ...But what has that got to do with your long life?
Embi: One of the problems with people here is that they do not take sacred vows at all seriously!
You are The Determinator. You have a mission in life, and you are going to accomplish it. You don't care how hard it is or who is standing in your way. You're going to do this, even if it takes a thousand ye...
What's that? It is going to take over a thousand years? Phooey.
Fortunately, thanks to a bit of Applied Phlebotinum, even this won't stop you from reaching your goal. If you need a thousand years, you'll find a way to live a thousand years, or ten thousand, or a million. However long it takes.
This trope is when someone is given an extended lifespan in order to accomplish a particular task. Until the task is accomplished, the character is immortal, but once it is, the character either dies or goes back to an ordinary lifespan. Sometimes this is a source of relief for the character because Who Wants to Live Forever? In other cases, Living Forever Is Awesome but accomplishing this goal is more important.
- Odago Koinosuke in Jubei-chan was given a command to find a successor to Yagyu Jubei, an oath he took with Undying Loyalty, literally. If in danger of failing his oath, he desiccates on the spot, and just as quickly revives.
- His daughter in the sequel has a similar impetus, except she turns into a tree should failure be imminent, and this is not done with as much aplomb.
- In Blade of the Immortal, an old woman specialized in giving kessen-chu, sacred worms who make anyone infested with them very hard to kill, and keep them as they were when they received this "gift". One way to remove these worms is to finish one important task.
- Panty & Stocking with Garterbelt: Garterbelt literally cannot die (he's surprised to learn this when he's brought back in reverse from an explosion) until he's fulfilled whatever mission God has given him.
- In Naruto, Orochimaru strives for immortality so he can learn all jutsu. According to his former friends, his goal was originally to live long enough to meet his dead parents' reincarnations. He became so obsessed with achieving this that he was willing to start crossing moral lines to become powerful enough to accomplish it, eventually becoming consumed by the pursuit of immortality and power as ends unto themselves.
- Takashiro of Betrayal Knows My Name takes a duras into his body in order to extend his life throughout multiple reincarnations of the villain. He tells the protagonist (also re-incarnated) that he intends for this fight to be his last, however.
- Sai from Hikaru no Go. He was a heian Go player that after commiting suicide haunted a Go board, possessing first the kid who will become Honinbou Shuusaku and then Hikaru, the protagonist. At first, the characters and the audience believe that this was due to him wanting to play Go even after his death and due to him wanting to achieve the Divine Move (a.k.a The Hand of God). Later we find that indeed there was a purpose for him returning as a ghost, but it wasn't his purpose; he was allowed to remain in the land of the living for him to be Hikaru's Mentor.
- In RG Veda this trope is played with Kaara. She was a human who was given the lifespan of a god by joining a god's Clan as a priestess, but she commits suicide out of guilt for not stopping her sister's betrayal. She's given a new purpose by Ashura-Ou, to protect the sword Shura-to until the new successor comes to reclaim it, and she waits 300 years for Ashura. Once Ashura takes the sword plus one of the sword's seals, she dies as the borrowed life she had was no longer needed.
- In arc 5 of Jojos Bizarre Adventure we have Bruno Buccellati who is killed early by the Big Bad, but due to his strong will it doesn't stick, though from that point forward he never bleeds or feels pain, and although characters notice this occasionally they rarely make comments aloud. However, at the end of the series he immediately passes away for good, having accomplished his goal.
- The Sorcerer Supreme is The Ageless — partly to give him a decent term of office, partly so that he can study and improve his mastery of the mystic arts without having to worry about getting sick, getting old, or dying. (Of course, he can still be killed...)
- In The Crow, the revenants resurrected by the title bird are resurrected and given invulnerability until they've avenged their own or their loved ones' deaths. The movies gave them an Achilles' Heel in the form of killing the bird in order to make them mortal again, which villains often try to exploit in order to give the climax dramatic tension.
- Marvel Comics has the Elders of the Universe, who are generally immortal because they have an overwhelming goal: collecting, game playing, combat, and so on.
- They are each the Last of Their Kind during the early days of the universe so they were granted this immortality. However, the most famous one, the Collector, lost his wife to Death when she found no more reason to live and her immortality failed her. As such, each of them pursued a never-ending hobby to give them purpose and not succumb to the same state of apathy.
- In the Petriculture series, it's established that Alicorns cannot die unless they actually want to - they are immortal and invulnerable until they are good and ready to give up their lives. Twilight Sparkle and Pinkie Pie vow not to pass on before Penumbra, because they don't want her to be lonely again.
- In Pages Of Harmony, Twilight intends to become immortal so that she can help harmony reign over chaos forever... after killing all the disharmonious through analyzing the Elements from her friends she killed.
- Inverted to horrific effect in A User's Guide to the Apocalypse. If you become a Death Seeker, you will be unable to die. It is only those who don't want to die, or who accept death as a simple inevitability, who end up dying.
- The Return of the Guardians trilogy spins guardianship this way. While a Guardian's strength comes from children's belief, true to the source material, immortality comes from performing their duties. Passing the job along to someone else gives them the opportunity to lead a mortal life. The Keeper is the second Father Time, and Angel is the fourth Cupid. Mother Goose declined immortality, and grew old and died without choosing a successor. By the end of the series, the Man in the Moon/Prince Ioniel names Jamie a candidate for her title once he grows up.
- The same counts here as in Comics. In The Crow it would seem that the same rules apply as in the comics. As long as the titular Crow is alive, the person they brought back is immortal and has a Healing Factor. This becomes a problem when Eric loses his immortality because he's already finished off every member of the gang who previously killed him and his girlfriend, but the crime lord who ordered the murder (and was thus indirectly responsible even if he might be the most culpable) is still breathing, so Eric's soul still can't rest in peace.
- In Indiana Jones and the Last Crusade, the Grail Knight is given immortality in order to complete his mission in regard to the grail.
- Balthazar Blake in The Sorcerer's Apprentice.
- It's implied (at least in The Film of the Book) that the reason Orlando never ages is because he promised Queen Elizabeth he wouldn't.
- In Santa Claus: The Movie, Claus and Anya (the future Santa and Mrs Claus) are given immortality along with their elves, so that they can make and deliver toys to the good children of the world in perpetuity.
- In Thor: Ragnarok, Surtur explains that he cannot truly die until he achieves his purpose of destroying Asgard during Ragnarok. Even if he is killed, he'll eventually come back. He eventually succeeds in his purpose, and he's apparently killed in the explosion that destroys Asgard.
- In the Animorphs Megamorphs book Elfangor's Secret, the team learns that in return to being sent to the past to complete a mission, one of their members will have to die. Later, after the death of one of them, the rest of the team discovers that they can't be killed, because only one of them was meant to die on the mission, making them effectively immortal until the mission is completed.
- In the Belgariad and related books, it's stated that wolves live "as long as they need to" and is implied that the same is true of sorcerers, given that they all have a mission from the gods to fulfill. But in the epilogue, none of them show any sign of getting ready to die off.
- In The Dark Is Rising, as a punishment for betraying the Light, Hawkin is forced to become the Walker and carry the Sign of Bronze for seven hundred years. He's hounded by the Dark all the while, until the time comes for him to give it to Will Stanton, the last Old One.
- Pete Hamill's Forever had a protagonist given immortality until he found his true love (as long as he didn't leave Manhattan).
- This is the basic plot of the Indigo books. Princess Anghara releases seven demons from the Tower of Regrets, and is made immortal so she can re-capture them all.
- Schmendrick from The Last Unicorn had a powerful magical gift, but none of his tutors were able to help him access it. Finally, out of frustration, one of the tutors cast a spell on him to make him immortal until he learned how to use his magic.
- The Lord of the Rings: Gandalf the Grey returns as Gandalf the White because he hasn't yet finished his job of making sure the good guys win.
- In the Morgaine Cycle, Morgaine set up the gates to reset the physical ages of herself and her companion Vayne as they pass through them, so as to complete their mission of closing all gates in the network in question.
- Glaeken from The Adversary Cycle and Repairman Jack novels lived for thousands of years without aging, so long as he was the Ally's champion. When he thought that he'd destroyed his foe Rasalom in The Tomb, his immortality left him and he began to age normally. Genre Savvy Rasalom had taunted him with the prospect that he might instantly age to dust if this happened, but the Ally wasn't quite so callous as to permit that.
- This is the reason for the anti-aging spell on the Palace of Prophets in The Sword of Truth series: The sorceress at the Palace can train a wizard, but not very efficiently. The spell is necessary to ensure that the wizards and sorceresses live long enough to finish the training.
- In one of the flashbacks chapters of the first Deverry novel, a young Prince Galrion, who had recently been renamed Nevyn, knelt before the grave of his ex-fiancee and swore that he would not rest until he had set right the mistakes that had led to her death, the death of her brother, and the death of another of her suitors. The gods made him keep that oath - he was around 450 when he finally died.
- John son of Zebedee, who in the Christ Clone Trilogy becomes one of the Two Witnesses, who then dies and is resurrected by God to enter into heaven.
- The Inquisitor from the Babylon 5 episode of the same name reveals he was originally kidnapped from late 19th century Earth, where he was better known as Jack the Ripper. The Vorlons kept him alive for the purpose of interrogating would-be messiah figures. When he actually finds two who are worthy of being the Messianic Archetype in Sheridan and Delenn, he says that he hopes he is finally done and that the Vorlons will let him die.
- Jiminy Cricket from Once Upon a Time. The Blue Fairy promises Jiminy that he will live as long as he needs to in order to help Geppetto.
- The TV series New Amsterdam had a similar premise to Forever (see Literature) with John Amsterdam, where he would live as long as necessary to find true love (he didn't have the "don't leave Manhattan" part). It led to some plagiarism accusations.
- Stargate Atlantis had an episode where an alternate version of Dr. Weir used suspended animation to extend her life long enough so that she could see to the maintenance of Atlantis from the time the Ancients abandoned it until the time the team arrived.
- The episode "The Vengeance Factor" of Star Trek: The Next Generation discusses a clan war in the history of the planet the Enterprise is visiting. A clan called the Lornak wiped out another clan, the Tralesta. To get their vengeance, the Tralesta survivors made their last member effectively immortal and made her the carrier of a virus to which only the Lornak were vulnerable.
- Richard Alpert is revealed to have been rendered immortal by Jacob, in order to serve as his Herald and carry his instructions to the Others. After Jacob's death, he remains immortal until a new protector of the Island is chosen, which coincides with his decision to finally leave the Island for good. As he does, he finds a grey hair, indicating he's begun aging once more.
- After becoming the new protector of the Island, Hurley offers Ben the same role. It's later implied they spent several decades or even centuries doing good work together, before deciding to move on.
- A darker version occurs with Michael. After leaving the Island, he discovers he is unable to die even after several suicide attempts, because the Island isn't done with him yet. Upon his return, he's finally granted his wish.
- In Dead Like Me, Reapers exist in a state of functionally immortal undeath, until they eventually move onto the afterlife.
- In the radio version of The Hitchhiker's Guide to the Galaxy, Wowbagger the Infinitely Prolonged at least thinks it's his purpose in life to insult everyone in the universe, and he does get his immortality revoked after insulting the last person on his list (the great prophet Zarquon). Does not apply in the novel (Life, the Universe and Everything), where he was made immortal in a random accident and gave himself the task of insulting everyone in the universe because he'd run out of things to do to pass the time.
- Older Than Feudalism: The Gospel of Luke in The Bible has an example in Simeon.
"Now there was a man in Jerusalem called Simeon, who was righteous and devout. He was waiting for the consolation of Israel, and the Holy Spirit was on him. 26 It had been revealed to him by the Holy Spirit that he would not die before he had seen the Lord's Messiah."Luke 2: 25-26
- Part and parcel of the Revenant Zombie. Revenants were the original undead, humans who died with a purpose so strong it could even override death, such as love or revenge, and could only die when their reason for coming back had been resolved.
- In Ramayana, it is said that Hanuman is immortal to sing praises to Rama, and will continue to be so as long as Rama's name is praised by anyone. That means Hanuman is virtually immortal until there's no devout anymore, from which at that point he would die and the world would go into a judgment day.
- Destroy the Godmodder: The reason the players of the series are invincible and can't be killed by the Godmodder is because the literal force that dictates the plot of every story in reality is on their side, giving them the ability to both do whatever they want and to not be killed directly (or at least, to have their deaths not matter much) just so that they can accomplish the titular goal, in a very extreme case of Plot Armor.
- The Risen Martyr class from the Dungeons & Dragons splat Book of Exalted Deeds resurrects a killed character, then kills them again as soon as they accomplish the goal they were resurrected for (or they reach the final level in the class and they can't multiclass further, though they can exploit the rule that says you don't have to level up). Intended for games with no resurrection but infamously bad in mechanics.
- Jefferson DeGrey in the Fantasy Strike universe was given immortality that will last until a vaguely-defined "true purpose" of his is completed. Until then, he is accompanied by a ghost woman who keeps him focused on finding out what that purpose is.
- Rose in The Legend of Dragoon is given a charm to prevent aging in order to have enough time to atone for a mistake made during the original Dragoon War (namely, releasing the Virage Embryo, a creature designed to bring about the end of the world).
- In Sly Cooper and the Thievius Raccoonus, the Big Bad Clockwerk tells that his hatred and desire for revenge on the Cooper family kept him alive for centuries. Gradually replacing all his body parts with mechanics helped, but it's revealed the only thing even keeping his mechanical parts going was his Hate Chip: a device that fueled him purely off The Power of Hate. With his Hate Chip destroyed, even his mechanics swiftly rust and decompose into nothing.
- The Magypsies of MOTHER 3 live as long as their needles aren't pulled, since its their job to guard their needles. Once their needles are finally pulled, they disappear.
- In Dragon Age: Origins, the Guardian of the Urn of Sacred Ashes implies that his vigil over the final resting place of Andraste will last as long as the Urn exists, or when the last bastion of the Tevinter Imperium finally crumbles into the sea.
- The protagonist of The Cat Lady is given the ability to revive upon death so she can confront and kill a series of serial killers known as "parasites".
- Taken up to 11 if you refuse the Queen of Maggots help to resurrect one last time, in which case Susan comes back just by being too determined to die.
- Inverted in Touhou with youkai, ghosts, and pretty much anything supernatural. They need a purpose to exist, so when they lose their purpose they try desperately to find a new purpose before fading away. Especially notable with the ghost Minamitsu, who has to drown people (or at least try to) in order to continue existing, even though she doesn't really have any grudge against her victims.
- Final Fantasy XIII-2 has Caius, who is given immortality so that he can be the guardian of the seeress Yuel in all her incarnations. He implies that he can be killed only by someone else worthy to be a guardian, who will then take his place. In the end, Noel ends his life, but without becoming the new guardian. However, the death is revealed to only have been temporary in The Stinger that's only seen upon getting all of the fragments, for reasons later explained in Lightning Returns: Final Fantasy XIII.
- Vhailor from Planescape:Torment is driven to enforce justice amongst the planes. The fact that he's long dead (his body has long since turned to dust) will not stop him from fulfilling his duty. If you point out to him that he's dead, Vhailor will point out that this doesn't matter: Evil exists, and evil must be punished. With very high Charisma and Intelligence you can point out to Vhailor that the number of already dead lawbreakers outnumber the currently living ones, causing him to pass on in hot pursuit of them.
- This also applies to Deionarra, whose spirit still remains bound to the world in order to help the Nameless One's quest. Turns out that one of the Nameless One's pastg incarnations tricked her into falling in love with him so that, when she died, her spirit would've stayed to help all eventual future (and amnesiac) incarnations. And he deliberately set up her death. This is regarded as one of the most evil acts in the entire story.
- In Dawn of the Dragons, this was forced upon the premium general Mathias the Masterer. The gods were disappointed in him wasting his vast potential, so they cursed him with an eternal life that would only end after he had mastered every skill in existence.
- In Undertale, this is what puts the "justified" in Justified Save Point. If you kill Toriel in the Ruins, and then reload to spare her, Flowey will reveal that he used to have that power himself, until you fell into the ruins — apparently there's a limit of one person with this power per closed system, and you're more qualified than he is — but he did keep the Required Secondary Power of Ripple Effect-Proof Memory. He elaborates on that toward the end of a worst-ending run, and steals it back from you at the end of a neutral-ending run. And in a good-ending run, you get a souped-up version as an 11th-Hour Superpower for the True Final Boss fight.
- During a worst-ending run, Undyne exhibits this to a degree when you first try to kill them. Their determination towards stopping you enables them to shake off death for a Heroic Second Wind, leading up to one of the hardest boss fights in the entire game. Too bad that if you defeat her, the second death actually sticks...
- And if you're going for the Golden Ending, the True Lab is full of failed experiments who cannot die due to being injected with Determination, which makes them immortal simply by giving them the resolve to live, no matter what.
- Drakengard 3 reveals that the series' Dragons have the power to reincarnate upon death. They can also sacrifice this power to grant a Wish. In other words, Dragons can live as long as they desire until they find something or someone worth dying for.
- In Dark Souls, undead characters have Resurrective Immortality so long as the Fire Flame is fading, but having a purpose keeps them from going hollow and losing their minds.
- Those held captive in the Well of Wonders in Sunless Skies are forced to perform in and attend to a theater play reenacting the story of a Prophet that tried to convince the Twin Kings of Eleutheria that a revolution might be a good thing. When at last the story managed to be told in its entirety thanks to your captain, they all crumbled instantly to dust, as they only had been kept alive and young to fulfill their role into reciting and hearing the complete story of the Exile Prophet. The sole exception was a little girl that became a very old woman as soon as the play ended, and died mere moments later.
- In Girl Genius, the circus performer Embi made a sacred vow to see the world before he died, over 130 years ago. He takes his sacred vow seriously.
- In Raven Wolf, the title tribe was cursed with removal from the sacred circle of life until the domestic civilization is ended. This means that they stop aging at maturity and if killed, their bodies don't decompose and their spirits cannot be reincarnated until the curse ends; they also can't hunt or cultivate crops.
- Rice Boy has those chosen to seek the Fulfiller: They will not die until the Fulfiller is found (as long they keep looking). In this case, it takes around 3,000 years. Of the three seekers, one continues on the quest until it is completed, one gave up long ago and performed a FaceHeel Turn (and has moved on to other life-extending means), and the last became disillusioned with the quest itself, and decided to let mortality catch up to him.
- In Tempts Fate, a B side comic to Goblins, the title character destroys a Demon who will take a thousand years to reform, after which the demon will enact revenge. However, as goblins only have a lifespan of 30 years, the demon "curses" him with immortality so that he'll still be around in a thousand years for said revenge.
- In El Goonish Shive, Abraham made a vow to destroy all the monsters the indestructible Dewitchery Diamond creates. He magically encases himself in stone (a la Human Popsicle) between incidents so he doesn't have to actually live through the intervening time.
- On Gargoyles, Demona and MacBeth are made immortal by the Weird Sisters as part of a plan by the Archmage to conquer Avalon.
- Both Demona and Macbeth agreed to become immortal (the latter also sacrificing youth to the former) in order to further their individual quests for revenge against a common foe. Appropriately enough, the terms of their immortality tie the two together in a cycle of revenge for hundreds of years. Only one can truly kill the other, ending both their lives.
- In The Legend of Korra, it's revealed that the Avatar's cycle of reincarnation was imposed by the spirit Raava in order to give him time to restore balance to the world. Apparently she has very high standards for worldly balance considering that the Avatar is still going cycle after cycle.
- In Rick and Morty, the Mr. Meeseeks are generated, given a single task to fulfill, then disappear, as they can't bear to exist for long periods of time. And they cannot disappear until that task is completed; they can be maimed, torn apart, et al, but they will keep going. Normally, this isn't an issue, but if they're given a truly impossible task, such as taking two strokes off of Jerry's golf game, bad things happen.
- DuckTales (1987): In the Five-Episode Pilot "Treasure of the Golden Suns", the character El Capitan is an elderly Spanish man. He found a golden valley (an expy of El Dorado called the Valley of the Golden Suns) but lost its location, and spent the next 400 years searching for it. He is extremely old and he looks old, but that won't stop him.