Sealed Evil in a Duel

Barbossa: So what now, Jack Sparrow? Are we to be two immortals locked in an epic battle until Judgment Day and trumpets sound, hm?
Jack: Or you could surrender.

—Pirates of the Caribbean: The Curse of the Black Pearl

Sometimes, the Big Bad is just too darned evil to be Sealed in a Can. Perhaps he already was, and it didn't work. After hammering him time and again, our hero eventually realizes that It's Up to Him, and carries out the Heroic Sacrifice Worse than Death: Trapping themselves in a duel with the bad guy for all eternity, thus effectively "sealing" their opponent with themselves as the plug.

If they aren't strong enough, the baddy will escape, possibly using its would-be impediment as a Soul Jar.

This can also be used as a Backstory, with the release of the Big Bad also releasing the original hero.

May invoke Someone Has to Do It. On the other hand, sometimes only their conscience is keeping them on the job.

Sister trope to Hell Is War. See also Kill Us Both; often overlaps with Enemy Without and Tailor-Made Prison. The furthest possible extension of How Much More Can He Take?. Might be the ultimate duty of a Barrier Maiden.

As a Death Trope, Spoilers ahead may be unmarked. Beware.

Examples of Sealed Evil in a Duel include:

Anime and Manga

The plot of Naruto commences with the Fourth using a variant of a sealing technique which summons a shinigami that devours both him and his opponent, damning them to do battle in its belly for all eternity. However, he used another technique with it that made the target (or maybe just half of it) instead become Sealed Evil in a Can. One wonders how the battle is going between The Third Hokage and Orochimaru's arms. It's also mentioned that it might just be a legend, and it probably just kills you. It's not like any of the previous users or victims of the technique, being dead/eternally sealed in a demon's innards, are in any position to tell anyone. However, the phrase "summoning contract" implies terms are spelled out between the summoner and summoned. If the contract stipulates the summoner is going into the summoned's stomach, then it will happen if you want the rest of the contract carried out. We eventually find out from Kabuto that souls being sealed in such a fashion do have a different fate than those who die normally, as it prevents them from ascending to the normal afterlife on a different plane which in turn prevents them from being brought back by Impure World Resurrection.
Getter Robo
- At the end of Getter Robo Armageddon, the original Getter heroes join an entire interdimensional legion of warriors dedicated to this. Though, considering that this iteration of the Getter team are pretty much a gaggle of Blood Knights, for them it's not so much Hades as Valhalla.
- In New Getter Robo at the very end it's implied this version of Ryoma also joined them.
The Jewel of Four Souls in Inuyasha turns out to be the souls of many demons locked in battle with the soul of a Miko. Kagome, the heroine of the series, nearly ends up trapped in the same situation, but manages to figure out the way to not only avoid that fate but also unmake the jewel and release the miko's soul.
Xam'd: Lost Memories ends with Nakiami sealing herself in the Quickening Chamber for a thousand years to offset the darkness of the Hiroken Emperor.
In Code Geass, it is subverted. Lelouch seals himself and the Emporer in the Sword of Akasha. It works out pretty well, with Charles having just gained immortality... until Suzaku arrives. Then it culminates with Lelouch destroying his mother and father.
- Of course, if things had gone according to plan, Lelouch presumably would have died of thirst, leaving the the immortal Emperor as plain old Sealed Evil in a Can.
Dragon Ball
- In Dragonball Z, when Gotenks says he won't be able to defeat Buu (actually a trick to distract Buu and a failed attempt at making himself look cooler in front of Piccolo by being a showoff and defeating him at the last second), Piccolo destroys the only door leaving the Year Inside, Hour Outside Pocket Dimension they're all in. Subverted in that Buu escapes by yelling and creating a space rip, and afterwards so do Piccolo and Gotenks by doing the same.
- In the movie Dragon Ball Z: Wrath of the Dragon, the antagonist convinces the heroes to gather the dragon balls to wish that a special music box he brought with him will be opened. He states that it has a trapped hero inside who will foretell of the coming of a great evil. This is all true, but he fails to mention that the great evil was bound to this hero, and by releasing the hero the evil is also released.
Yu-Gi-Oh!
- Pharaoh Atem seals himself in the Millennium Puzzle with Zorc Necrophades. Played literally as the two of them spend the next 3,000 years jousting over the most complex RPG known to man: human history!
- It is strongly implied that Yugi and Kaiba will keep on reincarnating and dueling against each other for all of eternity. Summed up in the Abridged Series:

Kaiba: Best. Destiny. Ever.

At the end of Puella Magi Madoka Magica, Madoka makes a wish to destroy every witch before they are born. In a strange sequence, she's told that she'll be locked in an endless battle with every possible witch. This is largely an Informed Ability, since we never actually see this happen - Madoka just causes magical girls to vanish before becoming witches. In fact the only witches we see her destroy are Walpurgis Night and her own witch. Notably, the manga adaptation seemed to change the line.
Claymore does it twice: once for Luciela, a former top warrior of the Organization-turned-Abyssal one, who is sealed away by her sister Raphaela (the two of them eventually become the Destroyer); the second time when dying Clare uses her last strength to seal both the Destroyer and Priscilla in a giant flesh cocoon, trapping them in a battle of willpower... for how long? No one is certain yet.
Done at the end of the Busou Renkin anime. Kazuki uses his Energy Release as a rocket to launch himself and Victor to the moon. Once there, they can't hurt anyone else but can never return until the rest of the alchemists get around to building a makeshift rocket.
Used in Tayutama. Mashiro seals herself along with the Tayutai to be there should they escape to recapture them all. The Tayutai aren't exactly evil (well, some are) but more playful and mischevious making them dangerous if let go.

Comic Books

The Justice Society of America did this when they fought the Norse Gods, to prevent Adolf Hitler from destroying the world with the Spear of Destiny. Justified as the battle was Ragnarok, which ended like this.
Once, after Doctor Doom came within an inch of wiping out the Fantastic Four, Reed decided the only way to keep his family safe from Doom for good was to trap the two of them in an inescapable pocket dimension. Knowing the team would never allow him to do this, Reed tried to distract them and push them away emotionally, but they managed to stop him anyway (unwittingly letting Doom escape). The kicker? Doom was already in Hell when Reed resorted to this—with Doom's record, he didn't trust the devil to hold him.
- and he was right! The comic shows Reed interrupting Doom in hell just as Doom was beginning to put a plan in motion.
- Another FF storyline, when they faced Reed's time traveling evil grandson Hyperstorm, ended with Hyperstorm trapped in a pocket dimension with Galactus, constantly blasting him with his own limitless energy to keep him at bay, but with Galactus feeding off the blasts. At the time, the FF assumed the two might be stuck that way forever, with Ben commenting that it was an awful fate even for a crumb like Hyperstorm. However, Galactus has since reappeared, which implies that Hyperstorm either found a way to escape or else Galactus ate him.
In the Transformers Generation 1 comic books, this is how the planet Cybertron and the planet-eater Unicron came to be—he and Primus were elder gods who battled across several planes, with the single-mindedly destructive Unicron winning the battle. As a last resort, Primus led Unicron from the astral plane into what is our dimension and directly into two metal asteroids, trapping both of them for eternity. While Primus turned his asteroid into the planet Cybertron, Unicron managed to turn his asteroid into a transforming planet-sized robot.
In Marvel Comics's What If of their crossover Atlantis Attacks, Set the Serpent God succeeds in freeing himself from interdimensional exile and returns to Earth, killing most superhumans and converting the rest (as well as regular humanity) to serpent people. One by one the remaining heroes and villains fall, and all hope seems lost, until Quasar arrives on the scene, having just escaped Set's dimension (where he'd been lost since the Serpent God escaped). He's been granted the Captain Universe power, which combined with his Quantum Bands to make him Set's equal. He opens the recently deceased Doctor Strange's Amulet of Agamotto, using it to pull them both into a pocket dimension where the two of them will battle forever. Unfortunately, although Set has been removed from the equation, he's had time to reproduce...
During the prestige format run of The Legion of Super Heroes, the Legion finally "defeated" the Time Trapper (the Anthropomorphic Personification of the Cold Universe cosmic model) by unleashing the Infinity Man (the Anthropomorphic Personification of the Cyclical Universe cosmic model) on him. The two end up locked in eternal combat with each other.
An Elseworlds posits that Batman and the Joker will be fighting each other in one form or another for eternity. Batman Beyond: Return of the Joker also supports this notion, at least until Terry kills him.
This is how Palpatine is ultimately defeated in the Star Wars Expanded Universe: Empatojayos Brand sacrifices himself so he can carry Palpatine's spirit away from the universe and in the custody of every Jedi who has ever lived, never to be resurrected again. He doesn't have to undergo Fate Worse Than Death himself, fortunately, but the effort of carrying away a spirit of pure evil does cause his own spirit a great deal of suffering.

Fan Works

Subverted in the Hunter: The Vigil fanfic "How I Learned to Hate Hiking". One character thinks that his yearly battle against a nature spirit is all that keeps... something bad from happening. Except that the enemy is the Spirit of Nature Getting Beaten by Civilization, so it uses this trope as a power source for an empathetic attack on humanity.

Film

Used as a Backstory in The Sorcerers Apprentice with both the Grimhold (with Morgana and Veronica) and with the Chinese vase in which Balthazar and Hovard get locked for 10 years.
- It's implied that Balthazar and Horvath didn't fight in the vase, as Horvath claims he was extremely bored, reading the same (poorly-written) essays on Napoleon over and over. You don't really have time to do that if you're busy fighting. At least Balthazar had his Incantus.
One of the many alternate endings for Freddy vs. Jason had the pair locked in eternal battle in an arena in Hell.
The Pirates of the Caribbean quote above lampshades it, but the duel itself manages to end when Barbossa becomes mortal again.

Literature

In Twilight Watch, Anton, The Hero, has to go up against an uber-powerful vampire. He's given various spells by the forces of both light and darkness, as well as the Inquisition. The spell given by the latter will encase the person its directed against in a tiny coffin wherein they will be alive for all eternity. However, the same fate will occur for anyone who casts the spell. Luckily, Anton doesn't have to use it.
Stationery Voyagers
- Emperor Alhox is actually destined to fulfill this role against Melchar, which is also why he is the only one capable of beating Melchar in open combat. (Levio is actually required to hold back his power negation if anyone else attempts to fight Melchar, allowing for a rare Diabolus Ex Machina protection clause to exist.)
- Also averted: Maurice can leave the Haragad Cavity whenever he wants, but is required to release Preamble from it temporarily near the end of time. (Same cannot be said of the Yehtzig trooper who was trapped in the cavity with Preamble...)
In The Book of the Dun Cow, Mundo Cani drives the Wyrm back into its prison inside the Earth where it's said that not only does he keep fighting to prevent Wyrm from invading the upper world, but that the souls of the brave go to join him in the battle when they die.
In Rick Riordan's The Red Pyramid, they deduce that this is what Bast was freed from, meaning that what she was fighting now has a chance. (She had to be; she was weakening, and needed to recover her strength.)
In The Sorceress, Aoife willingly triggers this to stop Coatlicue from rampaging across the myriad worlds.
In Riddle of the Seven Realms by Lyndon Hardy, Astron can only stop Palodad from destroying the multiverse by pushing the Big Bad into the flame that's tearing a hole in the daemonrealm, then jumping through himself and pulling the source of flame in after him. Subverts this trope, as Nimbia is able to create a new pocket-world within the Void to encase Astron, then retrieve him.
This is how the Penhaligon trilogy ends: Fain Flinn will fight Teryl Auroch forever to keep him from destroying Mystara.
This is how Superman wins against Saturn, The Devil's Agent on Earth in the novel Miracle Monday: by threatening to spend every second of the rest of his life fighting him and undoing all his evil deeds. (Actually, the book makes clear that Saturn could've won easily and destroyed the Earth if he wanted- but neither of those were his goals; he wanted to break Superman's spirit and end the hope he inspires in humanity. But just the realization that Superman would never give up effectively caused his defeat due to the laws that govern demons.)

Live-Action TV

Star Trek: The Original Series: In the episode "The Alternative Factor", Sane!Lazarus asks Captain Kirk to imprison him and his evil, normal matter counterpart in a time corridor, where both will remain fighting in a form of living death for all eternity. Since refusing to do this would put the universe at risk, Kirk reluctantly agrees to carry out this plan.
Stargate SG-1
- After season eight, Oma Desala vs. Anubis.
- Used again in The Ark of Truth: Morgan le Fay vs. Adria.
A nod to this trope was seen in the Doctor Who episode "Last of the Time Lords". After the decisive defeat of The Master, the Doctor was not willing to execute the only other member of his species in existence. So he volunteered to live up to this trope, keeping the Master confined in the TARDIS for all eternity or he reformed. The Master prevented this by committing suicide (or at least refusing to come back from the dead).
In the season 5 finale of Supernatural Sam combines this with Sealed Evil in a Can by inviting Lucifer to possess him, then trying to keep control of his body long enough to jump into the Can they have no chance of getting Lucifer into otherwise. Sam does end up jumping into the cage, with Michael (In Adam) falling in with him.

Tabletop Games

In Magic: The Gathering's Innistrad pack, the whole plot is driven by the fact the archangel Avacyn got herself trapped in the Helvault alongside her demon nemesis Griselbrand.
Legend of the Five Rings does this with Hida and his son, and later with Iuchi Karasu and Kuni Yori.
This is the origin of the Calim desert in the Forgotten Realms Dungeons & Dragons setting, in the form of a never-ending duel between a djinn and efreet lord.
Sisyphus shows up in the Fantasy Kitchen Sink that is Scion, and his specific case is subverted - when the Titans broke out, a rock took out the top of the mountain, letting him finally finish the job. As a result, he is now Nigh Invulnerable, possesses great power... and has no clue which side to sign on with. (If the Titans win, the world is screwed; on the other hand, three thousand years of pushing a boulder is a long time...)
Warhammer 40,000
- To stop the Thirteenth Black Crusade, Eldrad Ultharan had to trap his soul in a battle with the Chaos spirit powering Abbadon's Planet Killer. There is significant disagreement about whether he is dead or not, but being the most badass psyker in the entire setting he's probably still on that ship fighting it.
- Similarly, an Ork vessel once crashed on a planet in the Eye of Terror. Everyday, umpteen million Orks awaken and wage unending battle against countless hordes of demons until they die horribly, only to reawaken the next day. The Demon Lord in charge of the planet uses this to train and harden his army, except they keep getting killed and weakened; the Imperium thinks of this as a Fate Worse Than Death; the Orks consider this paradise.
On the Warhammer Fantasy Battle fantasy side, Caledor Dragontamer and his disciples have been trapped in the Vortex on the Isle of the Dead, where they have been stuck for at least 3000 years, ceaselessly performing a magic ritual designed to pull the excess magic out of the world and prevent (or at least massively delay) the victory of the Chaos Gods. In an interesting variation, the Chaos Gods are not on, or even touching the world near the Isle of the Dead (the closest being the overlap between the "real" world and the Realm of Chaos at the north and south poles), nor is any champion of Chaos present. It just happened to be where Caledor chose to set up his world-spanning spell.

Video Games

Kingdom Hearts: Birth By Sleep reveals in the secret ending that Terra is doing this with Master Xehanort as of the end of the story, both of them fighting for control of Terra's heart. Of course, a year or so later Terranort splits in two, his heart becoming False Ansem and his body becoming Xemnas; what they've been doing since then is anyone's guess.
- Probably still that. Neither of his incarnations use a Keyblade or show any sign that they actually remember being Master Xehanort, in full detail. However, the trailer for Dream Drop Distance implies that both of those are about to change....
Blizzard Entertainment likes this trope.
- It begins in Diablo. This is what the protagonist attempts after slaying Diablo's current avatar. Needless to say, it didn't work.
- In Diablo II: In the backstory (actually already in the first game's manual), Tal Rasha used his own body as an extension of a soulstone to imprison Baal. He is possessed, and has to be tied up and magically bound in a tomb, his spirit fighting Baal's for eternity. Or until Marius came along in the second game and tugged on the ringpull in an attempt to rescue Tal Rasha.

Tyrael: No! Don't do it!
(pop goes the soulstone)
Tyrael: Fool! You have just ensured the doom of this world!

- In World of Warcraft, Arellas Fireleaf, a minor character of whom we only know what is written on a statue, is said to be "Locked in eternal combat with the Necromancer Diesalven".
- A far more important example, if it is one: At the end of the Icecrown Citadel raid, Bolvar Fordragon dons the helmet of the Lich King to contain its power. This may mean that he's in there together with the original Lich King, Ner'Zhul, or that Ner'Zhul was destroyed or weakened to insignificance too and Bolvar is only keeping the armies of the Scourge at bay through his new control over them.
The cancelled Ultima X: Odyssey: When The Avatar sealed himself and his Enemy Without, The Guardian, behind a wall of life to destroy them both with an armageddon spell, The Guardian managed to merge with him. They then struggle for dominance with The Power of Friendship backing them up.
Blue's ending in SaGa Frontier appears to be him locked in an eternal battle with Hell's Lord after the portal to Hell is sealead away and the battle cuts away to a "The End" screen abruptly. Word of God says he teleported out, but that's not nearly as cool...
Quest for Glory IV has this with Erana and Avoozl. Ultimately, the hero's reason for being summoned is to finish summoning Avoozl, breaking the stalemate in favor of the Eldritch Abomination, only to free Erana who, now unbound, can banish Avoozl properly.
Freedom Force vs. The Third Reich: Manbot and the Wraiths of Chaos.
Persona 3: At the end, the Main Character sacrifices himself to transform into a barrier that keeps the two resident Eldritch Abominations from meeting each other and destroying the world.
In the Star Wars Expanded Universe, Jedi Master Lord Hoth uses this method to defeat the Sith Lord Kaan; forcing Kaan to activate a superweapon that trapped their spirits, and those of their followers, in eternal conflict and torment. Until Kyle Katarn released them, at least. This is all the result, though, of a Xanatos Gambit by Darth Bane, who sought to destroy Kaan's followers in order to remake the Sith in a superior form. Killing Hoth and numerous other Jedi was just a bonus, and they would be dead regardless of the initial fight's result.
In the Legacy of Kain series, Raziel, who wields the Soul Reaver wraith blade, discovers that the blade's soul is actually his own, and learns that he is destined to play out a Stable Time Loop for all eternity where he absorbs himself into the sword, is shattered and binds with himself, time and time again. The rest of the series' story involves him attempting to escape this predicament.
In one of the books based on City of Heroes, Statesman and Lord Recluse compare themselves to Sisyphus and the rock. Statesman wonders which one is which...
In Lost Odyssey, this is the fate Gongora wanted to avoid, cue the 30 years long Evil Plan. Of course, in the end, making 4 powerfull immortals very pissed backfire at the end.
As described by Noah Antwiler, ET the Extraterrestrial on the Atari2600 vs. the Player is pretty much this.
In Castlevania: Symphony of the Night, this is a brainwashed Richter Belmont's motive for reviving Dracula:

Richter Belmont: Count Dracula rises but once every century, and my role is over. If I can resurrect him, then the battle will last for eternity!

The motivation seems slightly different; as the above quote shows, Richter doesn't want to do this to trap Dracula (vs. letting him free); he wants to do this to continue the fight (vs. the fight being over).

Towards the end of Breath of Fire II, it turns out that the sleeping, giant dragon near the village of Gate is actually a Dragon Clan member, and Ryu's mother at that, who turned herself into that form to keep the game's Hell Gate closed and prevent the release of Death Evan. Slightly subverted in that you must relieve her of this task by going through the Hell Gate and defeating the Big Bad. If you choose not to, Death Evan immediately overwhelms her defenses and bursts to the surface, resulting in a Nonstandard Game Over. Even after Death Evan is defeated, demon gods don't just die. The Hell Gate has to be closed again to guard against his future return. If you failed to unlock the flying Township, Ryu himself has to take his mother's place. If you did unlock it? Turns out that a giant airship works just as well as a giant dragon for sealing a hole.
Shurelia's Heroic Sacrifice in Ar tonelico, to seal the Big Bad Mir. You get the chance to defy this. If you do, both Shurelia and Mir get better.
Mega Man Battle Network 6 has an interesting twist: There were two great beasts ravaging the world, so they enticed the beasts into fighting each other and then blocked off the battleground as best they could so noone would interfere or get caught in the crossfire (obviously that didn't work).

Western Animation

The 90s Spider-Man: The Animated Series
- Captain America and the Red Skull. Eventually, Electro joins them.
- From the same series, a sort-of-reformed Venom ends up jumping into a portal after his Evil Counterpart, Carnage, and since the portal closes after that, it's implied that this will be their fate. A Sequel Series saw them on another planet/dimension, though.
Jackie Chan Adventures ends with this, as the fifth season's Big Bad Drago (using the powers of all eight demon sorcerers) and his father Shendu (the Big Bad of the entire SERIES, using all twelve of his talismans) are sealed within another realm to duel for all eternity. Neither of them takes their fate very seriously. They spend their time bickering: Shendu chastising Drago for being an impudent child playing with his father's world (yes, Shendu still thinks Earth is his for the taking), while Drago whines about Shendu never being there for him because he's always busy fighting wizards.
One episode of The Fairly OddParents had a variation on this. Timmy wished Vicky wasn't his babysitter, and she became mayor of the city instead. Subsequent attempt to remove Vicky from power through wishing instead resulted in Vicky gaining even more power, up to the point of becoming a galactic conqueror. In the end, Timmy realized it's up to him to prevent all of these, and wished her to be his babysitter once again.
Adventure Time has Goliad, Princess Bubblegum's genetically engineered heir who'd gone mad with power and tried to take over the Candy Kingdom with her mind control powers, ultimately defeated by Stormo, another Candy Spinx created using Finn's DNA, sacrificing himself by locking her in a psychic duel with himself.