Long ago, An Ancient People faced a terrible evil. Using various methods, they bound the evil into a prison from which they thought it could never escape.
Sealed Evil In A Can, as the title suggests, is a way to introduce a villain suddenly, especially one that is legendary and powerful. It also explains why the villain hasn't done anything up to that point: It just now escaped.
Sometimes, the Big Bad's plan is to unseal the can of some ancient God of Evil; hoping they'll get some of that great power as a reward. If they succeed, it almost always turns out that the Sealed Evil was manipulating them into freeing them, making the Sealed Evil the trueBig Bad. Sealed Evil™ almost never rewards those who release it. It may act like the malevolent flavor of a Jackass Genie, twisting their releasers' wishes back on them, or it may simply decide that You Have Outlived Your Usefulness. Remember: Evil Is Not a Toy.
The primary question is usually "Why did they just seal it, as opposed to KILL it?" Well, the answer tends to vary; but usually it's a variant of The Punishment (for both the sealed and everyone else), and/or As Long as There Is Evil. Maybe it can't die (or more commonly, the conditions weren't right to deal the final blow), so sealing is the next best thing. Another common excuse is the Balance Between Good and Evil; if they'd killed the ancient evil, then a bigger, badder evil would've taken its place, thus sealing it away neutralizes the threat but also keeps it in the world and maintains the balance. For some reason, only on a very few occasions were the goods not strong enough at the time.
Expect the mere release of the SEIAC to cause a World-Wrecking Wave, Walking Wasteland, and sundry other disasters. That said, being cooped up for centuries is likely to have weakened the SEIAC, meaning it needs some time to recover its lost strength.
Since this trope can be traced back to Greek mythology, it's Older Than Feudalism. Notice that it is exactly the same, without the mystical magical mumbo-jumbo, as any plot where a horrible criminal escapes from or is released from prison.
This is an extremely common plot and backstory in video games because it's such a simple backstory: the Big Bad, put away by some ancient hero, has escaped. You (the player) must put him back in.
Polar opposite of Sealed Good in a Can. Sealed Badass in a Can and Girl in a Box are a neutral variant. See Sealed Inside a Person-Shaped Can when the evil is imprisoned inside a living being, Sealed Evil In A Teddybear when said person shaped can is The Team Pet, Sealed Army in a Can when the makers were low on cash and had to make do with a single can for multiple Evils, and Sealed Evil In A Six Pack when it's sealed within multiple things. Sometimes requires Sealed Evil in a Duel. Compare Tailor-Made Prison, when the current generation makes its own can to (temporarily) imprison evildoers. Compare Pointless Doomsday Device. For cases where a particularly powerful Sealed Evil overshadows a setting but never manages to affect the plot directly enough to be a Big Bad, see Bigger Bad.
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Ryoko, from Tenchi Muyo!, was sealed away as a traditional demon in the OVAs; however, after calming down by dueling Tenchi for an episode, she joined the cast as a protagonist and suitor for Tenchi's hand. Washuu was in a similar situation in the TV series.
In Yu-Gi-Oh!, Pharaoh Atem took the contingency plan of sealing both the Big Bad and himself 3000 years ago, until both resurfaced roughly simultaneously when their respective containers were found by archaeologists.
In Magical Girl Lyrical Nanoha A's, the Book of Darkness regenerates every ten years, sealing its programs (the Wolkenritter) inside of itself until then. Also, Gil Graham plots against both the heroes and Wolkenritter to allow for the Book, Wolkenritter and their innocent mistress to be sealed in the space between dimensions forever, because the Book would just keep regenerating. He is stopped and regrets ever deciding to put these lives at risk.
In One Piece, Impel Down, the world's most secure prison has a level that most people don't even know exists, Level 6 the "Eternal Hell" which contains at least two ex-Warlords of the Sea former Big Bad Sir Crocodile & Jinbe, Luffy's brother & Whitebeard Division leader Ace & Shiliew, the insane ex-Head Jailer who was a match even for Warden Magellan. And with the exception of Ace, all of these and more are free thanks to Luffy and Blackbeard.
In Dragon Ball, the original Big Bad, Emperor Pilaf, uncorks Piccolo Daimao ("Piccolo, King Of The Demons"), the Sealed Evil In A Can who had previously been trapped in a Denshi Jar by Mutaito-sama centuries before the start of the series. (The Denshi Jar gets bonus points for strangeness; it is, in fact, an electric rice cooker with a holy seal glued to it.) Piccolo is revealed to be a Gnostic version of Satan, being the pure evil that the current God expelled to get "pure" enough to get his position in the first place (oh, and God is a Sufficiently Advanced Alien). The trope is somewhat subverted, however, in that, one Cloning Blues and one Heel Face Turn later, Piccolo joins the good guys. And eventually even fuses with his "good" half when they desperately need a power boost.
Later, in Dragon Ball Z, the five-million-year-old sorcerer Babidi comes to Earth seeking energy to power Buu, the Sealed Evil In A Can that ate God's superiors. Originally, Toriyama wanted to finish the series after the defeat of Frieza, the ruler of the galaxy and the most powerful being in the universe. When the series' success made this impossible, he was forced to invent ever more implausible reasons why the ever more powerful villains hadn't shown up before and kicked Frieza's rear end. Androids, super-clones made from our heroes' DNA... by the time Babidi came to Earth, the current villain (Dabura) was the evil God of a Bizarro Universe. When he couldn't top that, Toriyama simply pulled Buu out of a Can.
Toriyama acknowledges his reliance on the Sealed Evil In A Can formula in the Neko Majin Z parody comic, in which the titular "hero" keeps a powerful demon sealed in a small rock balanced on top of a boulder by the side of a road. If anyone picks up the rock, the demon is released, requiring Neko Majin to step in and re-seal the demon... for a fee.
In the 13th movie, Wrath of the Dragon, the monster Hirudegarn is split in two and sealed inside Tapion and Minosha. Hoi breaks him free and rejoins the two halves... You guessed it, Hirudegarn stomps on Hoi and kills him. And Hirudegarn is eventually killed by Goku (who at that point used a technique that could have defeated him right from the start).
In the 9th movie, Bojack Unbound, the Galaxy Soldier, Bojack was sealed inside a star by the four Kais who would remain there. But due to North Kai's death by Goku's sacrifice with ready-to-explode Cell, Bojack was freed from imprisonment and heads towards Earth where Cell fought.
Slayers has Ruby-Eye Shabranigdo, which was broken into seven pieces and sealed in humans (and gets out every now and then), Zanafar, and for good measure Shabranigdo's lieutenant Chaos Dragon Gaav.
In Princess Tutu the evil raven was sealed away by a prince who broke his heart into shards; the raven gradually gains power through the series and is fully freed when the prince's heart is returned to him.
After "Him" in Powerpuff Girls Z is defeated horribly by a bunch of girls, he is contained in a tomb in an abandoned museum until the present day at which point he sends out a mummy to find the means to release him from his prison. His main goal is to conquer the world and destroy the Powerpuff Girls for their resemblance to the Ōedo Chakichaki Musume, the first three to defeat him.
The seal is played straight with Ryuukossei, however. The powerful youkai that killed Inuyasha's father is first mentioned only when it becomes necessary for Inuyasha to succeed in an achievement that surpasses his father so he can master his sword. Cue introduction of Ryuukossei who had never been mentioned prior to that point. Reason being that Inuyasha's father managed to seal Ryuukossei with a fang the way Kikyou had sealed Inuyasha with an arrow. Naraku frees Ryuukossei who fights Inuyasha and dies, allowing Inuyasha to surpass his father and master his sword.
Also from InuYasha, the Shikon no Tama. Unique in that it is both Sealed Evil In A Can andSealed Good in a Can. It contains the spirits of many demons that were once one entity and a powerful priestess locked in battle. Thanks to the efforts of Naraku, it gradually becomes wholly Sealed Evil In A Can.
InuYasha also features an anime-only example where the cast actually tries to seal away something evil to create this trope. When Toukijin's creator is killed as a result of the sword possessing him, the sword lands in the middle of a field. Even Ultimate Blacksmith Toutousai is unable to approach its immensely powerful evil aura, leaving them at a loss what to do. In the manga, this is the moment where Sesshoumaru (who commissioned the creation of the sword) arrives, defeating and mastering the sword as soon as he touches it. In an Adaptation Expansion, the anime, has the blade begin to corrupt the ground around it as soon as it lands, spreading swiftly. Since none of them can approach it, they debate what to do and Miroku decides to build a small shrine around the sword, blessing it to keep Toukijin's evil from spreading. Only then does the anime allow Sesshomaru to arrive to defeat and master the sword.
In the third movie, the evil sword Sou'unga was also sealed away for a few hundred years, only to break the seal while in Kagome's time and go about trying to kill everyone.
The anime version of Prétear starts with the villain breaking free after sixteen years of being sealed away.
And in the manga version, she remains sealed—but still manages to possess others anyway.
Most of the villains in Sailor Moon were sealed until recently, except for the last season. In the first season, inside the can (the Dark Kingdom/Negaverse) was another can, with another, bigger Sealed Evil (Metallia/Negaforce) inside it; the forces of the Dark Kingdom spent most of their time draining energy from people in order to charge the metaphorical can opener needed to release her.
In the last season (in the anime at least), it is revealed that at the end of the first Sailor War, Sailor Galaxia had sealed Chaos inside her own body.
In the Gonzo version of Hellsing, the final episode reveals that Incognito plans to release the Egyptian god Set in order to destroy the world. Alucard defeats the released Set, it is left ambiguous if Set was really destroyed or just resealed.
Alucard himself used to be in a state of hibernation as a dead, rotting husk in a basement. And then someone found a way to splatter him with blood...
In Soul Eater, the Sealed Evil in a Can is the Kishin, an insane creature who wreaked havoc upon the world until being sealed. The people working for the Shinigami do so to prevent the creation of another Kishin, which would occur if someone consumed a large number of human souls. It is not until half-way through the series that the main characters discover that the "original" Kishin is still alive, and imprisoned underneath their city.
Not only does said Evil get out, but the manga later reveals that there are similar creatures trapped elsewhere, although the Great Old One in Eibon's book has more in common with Shinigami than their estranged comrade Asura.
In Deadman Wonderland the "evil" are people affected by the "Branch of Sin" dangerous blood-manipulating powers who are secretly hidden deep in the "can", a maximum security prison/publicly open amusement park
Mahou Sensei Negima! features two examples, one completely straight and the other a little bizarre. First, as the straight example we have Ryomen Sukuna no Kami, a gigantic four-armed two-faced demon god sealed in the Kansai region of Japan; releasing and controlling him was the motivation for the villains of the Kyoto arc. Second, and rather more unusual, we have the ancient and legendary vampire sorceress Evangeline A.K. McDowell. While she was a wanted magical criminal, responsible for multiple heinous crimes and with a huge bounty on her head, her sealing was based less on her evil and more on her obsession with the main character's father. And, once you get to know her, she's not really as evil as she liked to claim... to the point that when the aforementioned demon god is released, the protagonists defeat it by breaking the seal on Evangeline and letting her deal with it.
Played straight again with the Lifemaker, the ultimate Big Bad of the setting, who is sealed inside the Sacred Tree of Mahoro Academy.
The 3 big bad Tayutai in Tayutama are strong, but their method of sealing might have needed to be reinforced. They were freed by a runaway moped. On the other hand, it let Mashiro out into the world, so it all balances out.
In Umineko No Naku Koro Ni, Beatrice; The Golden Witch, The Endless Witch, The Witch Who Has Lived For A Thousand Years; is set up as this. However, the longer the story goes on, the less that seems to actually be the case. According to her the can she was sealed in was originally meant to seal something else. This is also most likely not the case.
In the third part of Jojos Bizarre Adventure, legendary antagonist Dio Brando is released from imprisonment in a casket at the bottom of the sea by some unwitting salvagers, where he'd spent the last 100 years since the end of part one.
In Bleach, this is Big Bad Aizen's final fate, as he's put in jail for 20,000 years.
Tailed Beasts in Naruto are generally Sealed In Side A Person Shaped Can because it lets people use their power, there are a couple cases where they've been sealed inside objects: Shukaku was said to have been sealed in a teapot, the 8-tails was sealed in a giant jar (which can seal people in it as well), and after removing the Ten Tails chakra the Sage of the Six Paths sealed it in stone and put it in the sky, creating the moon.
After acquiring chakra material of all 9 Tailed Beasts, Tobi/Obito uses the Demonic Statue of the Outer Path as a vessel for its resurrection.
The manga has subverted this recently. It's been revealed that the tailed beasts aren't inherently evil, it's just that most of them hate humans due to (repeatedly) being used by them throughout history. Killer Bee, and later on Naruto, eventually get the beasts sealed in them to make a Heel Face Turn by actually respecting them as sentient beings rather than treating them like mindless monsters.
In Digimon Frontier, Lucemon was sealed away in the Digital World's core. Some time later, he ends up using the Royal Knights to scan the entire Digital World and its three moons, effectively vaporizing them, to break free.
Zeref of Fairy Tail is revealed to be this right after someone wastes their life trying to raise him from the dead.
Even worse, the guy who wasted his life was just a diversion while someone else got the keys to unseal Zeref, who reveals later that he was never even sealed. He also isn't really that evil in the present.
Liselotte Werckmeister in Eleven Eyes was sealed by the Black Knights in a Crystal as she is an immortal and intends to destroy the world. Though in the finale of the story, the seal is undone. In the anime only ending, once again she is sealed away to a spacetime rift with Kakeru and the black knights combine effort. In the original game novel, Kakeru manage to finally kill her off for good by destroying the Voidstone within Liselotte using the Eye of Aeon.
Mag Mel/Emperor Barodius and Razenoid/Dharak started the fourth season of Bakugan as this. Credit must be given to Code Eve for being extremely thorough though. He was sealed inside armor crafted from his own evil, then imprisoned in an alternate universe, and tied to his own throne with powerful webbing. The only reason he was able to free himself was simply because he had a Psychic Link to Dan and Drago, allowing himself to become powerful enough to free himself, something the one who put him there wasn't aware of.
The ghosts of Ghost Stories, until the construction sites destroy the places where they had been imprisoned. Satsuki then has to spend the rest of the series re-sealing them.
For a much older example, consider the Bottle of Suleiman, which upon being sacrificed has a 50/50 chance of either releasing a fairly powerful djinn that joins your forces or else simply blowing up in your face.
And then there's the Tomb of Urami, who nets you a big demon at the price of sacrificing all of your lands.
Yawgmoth, the guy who makes planeswalkers look like muggles and Dominaria's version of the Devil, was sealed in a whole other plane back when he was a mortal. He wanted back in and spent thousands of years in a battle of wits with Anti-Hero Urza with his freedom as the stakes.
In the Zendikar expansion a group of Eldritch Abominations called the Eldrazi were got sealed away by Sorin Markov and two other guys, turning all of Zendikar into a prison for them. The final set in the Zendikar block, Rise of the Eldrazi, sees them loosed on the Multiverse.
A plot-relevant example can be found in the Innistrad expansion: The Helvault was created by the archangel Avacyn to seal away demons that she couldn't outright defeat. The plot of the expansion is set in motion when, by twist of fate, Avacyn herself becomes sealed inside the Helvault.
Yu Gi Oh! has several monsters like this, the most memorable being Exodia (who is split up into five pieces and allows you to win the game should you have all five in your hand; in the anime, it did take a huge ritual to unseal it) and all versions of the three God Cards (Egyptian, Sacred Beasts, and "Wicked Gods", all of which need three sacrifices to bring out and have devastating power, and two of which have fusions of themselves that are even more powerful). In the anime, they are so powerful that most of them are sealed up themselves, and it's considered madness for anyone to try and duel with them in their deck.
In The DCU, the Phantom Zone is essentially an other-dimensional prison that holds numerous Kryptonian criminals. As such, there many stories where the prisoners escape and the heroes have to fight to throw them back into the Zone.
In Hsu and Chan, the Tanaka brothers fight off a demon invasion by sealing them in various trinkets and keepsakes.
In Lucifer, the seraph Meleos long ago created the Basanos, a living, extremely powerful living tarot deck as both a complement to Destiny's book (which contains nearly everything that will ever happen) and a means of recording and preserving humanity's thoughts. The latter function, however, corrupted the Basanos and turned them into beings of pure evil, so Meleos has since locked them in a box. However, when Lucifer demands the use of the Basanos for divination, Meleos resolves to destroy them and opens the box, whereupon the cards overpower him and escape.
In The Astounding Wolf Man Gorgg is an ancient and evil golem that was imprisoned under Stonehenge. As soon as he is released by The Face he goes to kill the blood relatives of those who imprisoned him.
Green Lantern: Rebirth revealed that the long-established "yellow impurity" in the Central Power Battery was actually Parallax, the "yellow fear entity," an insectile manifestation of that emotion, released when Hal "Greatest GL of them All" Jordan entered the Central Battery years before.
Justice League of America comics occasionally feature early JLA enemies the Demons Three (Abnegazar, Ghast, and Rath), evil beings who ruled the Earth a billion years ago until being imprisoned in crypts by mysterious powerful entities called the Timeless Ones. The three Demons were eventually summoned/released in the present by Felix Faust, with occasional other escapes from imprisonment since then.
Parodied in a 1983 nine-page story in Love and Rockets by Jamie Hernandez called Maggie vs Maniakk. Maggie plays with a "Mayamese mini transporter" and accidentally frees Maniakk, a costumed super evil trapped in limbo/the ninth dimension by Ultimax, a superhero now down on his luck.
In "The Garden" segment of Garfield: His 9 Lives, Garfield (who is a kitten here) and Cloey (his owner in this life) are given a magical garden by Uncle Tod when he joins the circus, under the condition that they never open the crystal box on the checkered toadstool. The trope is subverted here because, out of loyalty to Uncle Tod, they decide not to open it.
Fables' second Big Bad came out of his can due to the effects of the heroes saving the world.
Also, the djinn that Frau Totenkinder dealt with earlier, although that was more of a case of amoral and incredibly dangerous and destructive, especially in the hands of an evil man, but not evil in and of itself.
Lampshaded in the short-lived comic BMG, where the Big Bad releases The Dragon from a can labeled "Instant evil. Just add water."
One episode of The Sandman had an Arabian Nights-flavored tale with a medieval caliph (kind of like a Muslim king/pope) who wanted to talk to Dream. The caliph went into a dark secret room and took out an ancient globe full of demons, threatening to break it and release them all. Morpheus appeared, took the globe and pocketed it, and then inquired what the caliph wanted.
Superman. Doomsday was living Sealed Evil, but ultimately broke out of his own can. He keeps getting re-sealed in stronger cans (we hope!). The DVD movie cartoon "Superman: Doomsday" is a more literal version of this trope, as Doomsday was accidentally freed by Lexcorp.
In Marvel comics, Galactus acts as a can on a greater, multiverse-destroying evil. Most of the energy he gets from his food goes to maintaining the seal, explaining his unusual diet.
The Warlock Graveyard in I Hunt Monsters is this, housing many powerful monsters in it and kept in check by an obelisk that needs to be recharged every century of so. It the protagonist's disbelief and reluctance that ends up freeing the monsters and he forced to track them down and re-seal them.
Jurid from Thieves And Kings, also known as "the Dawn Swallower", is a powerful monster, but spent a thousand years or so stuck in a glass bottle, trapped by a young girl.
Zom, from Doctor Strange - a surprisingly obscure hyperdemon who was sealed in a special amphora in another dimension. Horrifically powerful. He was initially imprisoned by a coalition of cosmic beings, including Eternity and frickin' Dormammu, and when he was let out, he frightened Umar (Dormammu's even scarier sister) so much she ran home and said she'd never come out again. Considering how bad-ass he is, the "can", or amphora, must truly be the can of the gods.
In the comic strip Wormy, the titular dragon owned a collection of magical orbs containing vicious demons, which a human wizard attempted to steal. This being a humor comic, Wormy used the orbs as snooker balls.
The Source Wall in The DCU is a huge cosmic barrier between the Source (the source of power behind existence itself) and the rest of creation. The Wall is decorated with the bodies and visages of all of the would be conquerors who have sought to claim the power of the Source for themselves, imprisoning them for all eternity. The Wall is one of the more effective Cans in fiction and only three people have ever escaped it. One of them, Yuga Khan (the father of Darkseid), managed to summon just enough power to free himself from the Wall...only to get himself imprisoned in it again in another bid to obtain the Source, this time for good. The second one was Darkseid himself, and he needed the help of the one who imprisoned him in the first place (Superman) to do it. The third was Superman, who was trapped by Darkseid and required the help of every variation of Supergirl from the last twenty years to break free.
In the conclusion of The Thanos Imperative event, the now immortal Thanos is trapped in the Cancer Verse. Star-Lord and Nova trapped him there along with themselves to keep him from destroying their own universe in his rage at being forever denied the embrace of his beloved Death.
Tiamut the Dreaming Celestial was exiled to Earth by his Celestial brethren for committing a crime against "life itself". Later revealed to be a case of Sealed Good in a Can. Tiamut objected when the others tried to cull the Deviants of Earth, and was punished for it. The Deviants understandably worship Tiamut as their savior.
The french comic book Les Légendaires introduces the Evil God Anathos, whose essence was trapped a long time ago by the other gods in a living prison called the Bearer. While his origin is a typical use of the trope, the way he comes back is partially subverted, as he frees himself by taking control of the Bearer and using Demonic Possession, as well as manipulating one of the protagonists rather than another villain; the original Big Bad, Darkhell, actually attempted to prevent his return rather than helping him.
In Earth 2, Alan Scott defeats Grundy by putting him in a place where there is no life for him to corrupt. Namely, he puts him on the Moon.
Loki's first appearance shows him imprisoned inside a tree. He would become free only if his captivity causes someone to shed a tear. No one missed Loki strongly enough to want to cry, so he forces Heimdall to shed a tear by poking him in the eye with a leaf.
Another example of this in The Mighty Thor franchise is Mangog, the sum total of the hatred of a race that was slain by Odin. It was imprisoned with a warning on the door until released by the Rock Troll Ulik who thought it would be an ally against Asgard.
Then there were older foes of Asgard imprisoned by Odin. Ymir the Frost Giant, Surter the Fire Demon, and Skagg the Storm Giant, the last two were released by Loki to attack Odin.
And more recently, there's The Serpent, God of Fear and Odin's brother, who Odin sealed in a prison at the bottom of the ocean ages ago, until freed by Sin (who had been transformed into one of his Worthy).
In Fuck The Jesus Beam, BaROCK Dominatus Caesar Inferno Vespucci Giovanni Goku Super Sexy Awesome Absolute GOD O.B.A.M.A., officially known as the greatest evil the world has ever known, is a Kenyan terrorist who was president for 14,657 consecutive terms and started 95 world wars who has been sealed away for 100 million years. Niamy releases him to deal with the Bombignats and Fetii, only for him to take control of them.
The Touhou fanfiction Imperfect Metamorphosis has both Rin Satsuki and the Shadow Youkai, who were sealed in the different ways and for different reasons, although while they're both thought of as evil only one of them actually is. The characters involved in the sealings also spend a lot of time justifying them, which ultimately boils down to the two being too damn tough to kill and requiring a different method.
The Powers Of Harmony has Nightmare Moon's corrupted army, which was sealed in Tartarus. Keeping them sealed, and then preventing Cetus from releasing them, is a driving part of the plot.
Discord is also mentioned several times. Turns out, Harmony is trying to arrange his release simultaneously to her own, in order to purify them both and restore their balance.
Demon Of Wind: This gets discussed in the story between characters as to why so many great evils are locked away instead of outrightly destroyed. It is also played with in the case of Rai who, though being locked away for being part of the bad guys, was at worst a Punch Clock Villain, albiet an alarmingly effective one.
In addition to Discord (who is imprisoned as in canon at the beginning of Reharmonized Ponies), the Pony POV Series has several others. One is Morning Star, Celestia's Fallen Alicorn brother, who was imprisoned for trying to take over the universe after deciding he was better than the Elders and being as evil as Discord if not worse. He was released by Havoc to fight in the Alicorn/Draconequi War, where he was either killed (though considering Evil still exists, he wasn't killed as thoroughly as it's possible to kill a God) or imprisoned in Hell (Havoc's domain) after the war as part of the peace treaty between the two according to Word Of God. Another recurring one is Grogar, a G1 My Little Pony villain and (in this series) DarkseidExpy who is sealed away in another dimension. It's stated he returns every five hundred years unless stopped and has to be resealed. In his case it may be justified because, in Dark World, he's been shown to be powerful enough to go toe to toe with Discord and have a chance of winning, as well being extremely Dangerously Genre Savvy. Discord shows a great deal of anger that Grogar doesn't seem all that mad about this, in direct contrast to Discord himself, who can't stand his can.
There's also the Shadow of Chernobull, an entity created by Pandora and then locked in her Box, until a Hooviet experiment accidentally freed it, leading it to feeding on the Hooviets' existence and desires for a Super Soldier, becoming General-Admiral Makarov (Big Bad of Shining Armor's side-story).
Time Lords and Terror: The plot is driven by Hydia's attempts to unleash the S'muz, in her misguided belief that it will aid her in her plans. She manages to free it, but after it kills her, the Mane Six proceed to use the Elements of Harmony to destroy it.
Titan from My Little Unicorn, at least till he breaks out from his dimensional prison.
Film - Animated
Jafar in Disney's Aladdin and The Return of Jafar.
The villain Hexxus in FernGully, who for ages was sealed into a tree, and was released when the tree was cut down.
The Titans in Disney's Hercules film. Zeus imprisons them all beneath the ocean with lightning bolts, but when the planets align, Hades is able to release them. Hercules uses the Tornado Titan to suck the other Titans in, then throws them all into space where they explode.
Superman and Superman II both feature the Phantom Zone, but make it out to be a one-time prison for a specific set of three villains.
In the movie The Ruins, as well as in the book, the protagonists are attacked by a sentient, carnivorous, and parasitic vine living on an ancient pyramid (or in a mine shaft, in the book). The vine is kept on the pyramid by a ring of deforested and salted land carved out of the jungle around it, and is effectively sealed up by a very stringent quarantine set up by the villagers living nearby. In the end of The Movie, one woman manages to escape, but it is hinted that the vine is living inside of her, and in one alternate ending, it is directly shown that she has taken the vine with her back to civilization, unsealing the evil and letting it go free.
Wishmaster is this trope. A powerful djinn sealed inside a fire opal since biblical times is awakened by the heroine who accidentally broke it. The monster will wreak havoc on earth as soon as the girl ask her proverbial 3 wishes. But she wont, 'cause that would be wrong. And so on.
John Carpenter's Prince of Darkness had sealed evil in a can — Satan, in fact, sealed in a giant glass and metal container in the basement of a church. He escapes.
And then there's The Thing (1982), sealed in a block of ice until some ill-advised Norwegians dig it out.
2001's sequel, The Mummy Returns, opens up another can of evil in the form of The Rock's CGI-animated appearance as The Scorpion King — which in turn opened the door for one of those prequels mentioned in the main text.
Averted in the third Mummy movie, when the already incredibly powerful Chinese Emperor didn't gain anything from the curse that transformed him into a crumbling clay figure. In fact, if it wasn't even the curse that revived him, but some miracle water. As a side effect, though, he has the ability to throw his face at people. He used it.
The Van Helsing movie has Dracula sealed inside his own part of the world, but circumventing it by developing wings, which he passed on to his other kin.
In the 2007 Transformers movie, Megatron is kept on ice inside the Hoover Dam, and is pretty angry upon thawing out.
Prequel comics for the 3rd film reveal Shockwave to be this; he was found by the USSR decades ago. And there's Sentinel Prime, who's been locked in stasis on board the Ark, which crashed on the moon.
The comic books as well as the movie adaption of Hellboy feature several such sealed-away monstrosities. In the movie, one demon was sealed in a consecrated urn, and the Ogdru Jahad, the Lovecraftian chaos gods of the Hellboy universe, lie imprisoned and waiting in the Void beyond the stars.
In the first Ghostbusters movie, the Ghostbusters seal all of their captured ghosts in a large containment unit that can only stay locked through the help of a power grid. When they capture an individual ghost, they suck it into a smaller container. And it then gets unlocked.
The Big Bad of the sequel is a 16th-century despot whose spirit inhabits his portrait.
In Clive Barker's Hellraiser, the Cenobites will not come after you unless you solve the puzzle of the Lament Configuration.
In Gremlins 2 The New Batch, Billy traps the Electric Gremlin in the Clamp Corp. phone system, where the villain suffers the torture of being on-hold.
In Mighty Morphin' Power Rangers: The Movie: The Movie, the shapeshifting Ivan Ooze had been trapped underground for 6,000 years until his containment chamber was accidentally unearthed by a construction crew and later opened by Lord Zedd.
The titular monster of The Beast from 20,000 Fathoms, while more predatory and aggressive than actually evil, is certainly an example of this. The rhedosaurus was frozen in Arctic ice since the early Cretaceous, and is thawed out by nuclear testing. Somehow, it is still alive.
Also, Evil himself is unable to leave his fortress.
Played with in the film adaptation of The Shadow. A museum receives a silver sarcophagus from a mysterious source, with an inscription on it saying it's the coffin of Genghis Khan. When the security guard is left alone with it the coffin starts to shake around and eventually opens up to reveal a man in the dress of a Mongol warrior, who telepathically forces the security guard to shoot himself. However, it turns out it's not actually Genghis Khan, but a modern-day descendant.
Living Hell, a recent horror movie has sublevel 4, vault 12, on a military base, which the protagonist doesn't want disturbed. The military had completely missed the hidden door in the vault 'til the protagonist waltzed in and told them there was something there... and we all know what to do with hidden doors, right? So, nice job there, hero.
Played with and subverted in Kung Fu Hustle. The Beast is locked up in an insane asylum — but only because he was bored from the lack of worthy opponents to duel and so checked himself in. When Sing is snuck in by the Axe Gang to break out the Beast for recruitment and picks his cell door open, the audience sees the Beast as a bald old man with a pair of spectacles in wifebeaters and boxers sitting on the john reading a newspaper. Which makes the Beast Sealed Evil On the Can.
The crew of the Enterprise almost let Evil out of its can in Star Trek V. "What does God need with a starship?"
The Blob has the heroes create a sealed evil in a can out of the titular menace by freezing the monster and transporting it to the north pole. And now we have Global Warming...
The sequel Beware The Blob: a oil worker brings home a frozen chunk of the Blob, sealed in a thermos. But not sealed too tightly or else we wouldn't have a movie.
In The Mighty Boosh Live, the Hitcher and his minions are introduced into the show when a box is opened. The Hitcher was apparently sealed in the box for 200 years, for crimes against humanity.
Including, but limited to raping a dolphin and driving contaminated swans to fights.
In Return of the Living Dead, a brain-eating zombie and corpse-animating 245-Trioxin gas are accidentally released from a sealed metal canister.
The Thief of Bagdad, directed by Alexander Korda, provides a classic example, lifted from the old Arabian Nights tale, "The Fisherman and the Bottle"; Abu the thief, stranded on an island by Jaffar, finds an old glass bottle and uncorks it, releasing a huge genie, who had vowed long ago to kill whoever released him from the bottle. Abu tricks the genie back into the bottle, prompting the genie to offer the prerequisite three wishes. He turns out to be a bit of a Literal Genie.
In the Mother of Tears, Mater Lachrymarum's powers are restored by the unearthing of a lost talisman, making it more a case of "Sealed Evil Artifact In A Can." Lachrymarum herself was apparently in some sort of self-imposed hibernation prior to this.
In Jumanji, the titular board game is buried underground for decades until it is unearthed by a construction team and found by Alan. "What if someone digs it up?" "Then may God have mercy on his soul."
Rare Exports A Christmas Tale: In prehistoric times the Sami-folk of Lapland, tired of the tyranny of Santa Claus, lured him on weak ice, and he sank to the bottom of the lake, which subsequently froze through. He was cut out and covered with tons of sawdust to keep him from melting, and then layers upon layers of dirt and stones over the centuries, until the Korvatunturi mountain on the border of modern Finland and Russia was formed. And this Christmas an obsessed American millionaire decides to dig him out. He is not happy.
Beetlejuice. The title ghostly con artist is trapped in the afterlife. He can be temporarily brought back to the real world (and returned) by saying his name three times, but can only be truly free if he marries a human female.
The Keep: An ancient monster has been trapped in a castle for centuries, until some Nazis awaken it.
Quatermass And The Pit has an ancient alien evil buried under London for millions of years, finally unearthed by building works.
Uwe Boll's Alone in the Dark (2005) has this, though watching the movie it can be hard to tell exactly what it is. The movie talks about a dark world that mirrors our light world, but at other times, it suggests that the Abcane tribe that discovered them ARE the evil in the can. But then, it's Uwe Boll, so...
And the other Morganites, including Morgan Le Fay herself.
The Last Lovecraft: Relic of Cthulhu has the titular Cthulhu himself sealed (by choice) somewhere under the sea. The last remaining Lovecraft must guard the relic of Cthulhu to prevent it's awakening.
A ridiculous number of these show up as non-Darklord threats to harass poor Lone Wolf. In a slight subversion, one of these sealed evils, namely Darklord Vashna, the most powerful Darklord of them all, who even tried to play The Starscream to Big Bad Naar in the Back Story, is already dead. Not sealed alive in a prison somewhere, but dead. The goal of two of the books in the series (The Chasm of Doom and The Legacy of Vashna) is to prevent him from coming back.
Lord Zahda in Castle Death is another interesting example: he's definitely a powerful evil who had been sealed away, but not so much in a can as in a castle on an island which he ruled over, where he had subjects of his own. So a much larger, more comfortable can, at least.
At the end of book 3, The Caverns of Kalte, you are the one doing the sealing, when you exile Vonotar the Traitor to the Daziarn Plane by pushing him through a shadow gate. The Daziarn is a whole dimension of its own, not really a can, and you would eventually see Vonotar again.
The Deathlord of Ixia was a more conventional example, since he really was sealed in the proverbial can, and then escaped.
Agarash the Damned, Naar's most powerful champion of evil, was sealed in another dimension by the Elder Magi millenia ago. In the Grey Star books he is the Bigger Bad goading the Big Bad Shasarak into freeing him. Grey Star has to prevent this.
North Korea in World War Z. One day, in the early stages of the Zombie War, the entire country simply disappeared - DIA spy satellites stopped picking up any activity or indeed signs of life within the Democratic People's Republic. The best bet is that the entire population relocated to massive underground bunkers. Nothing has been heard since, which means one of two things: Either one of them was infected, or none of them were. In the former case, that means one of two things: either they controlled the outbreak, or they did not. If the didn't, then 24 million Zombies are waiting beneath the surface, trapped in the tunnel system, and Communist architecture - well, it ain't all that good. If no-one was infected and/or they managed to control the outbreak, then 24 million fanatical, nuclear armed fascists are waiting on one side of the Korean DMZ, and when they find out how weak the rest of humanity is...
19th century example: The 1842 German novella Die schwarze Spinne (The Black Spider) by Jeremias Gotthelf: heavily steeped in Christian-conservative symbolism, the story, based on folktales, contrasts pastoral life with satanic influences. The titular black spider (a metaphor for the Black Plague) is created when a ruthless knight baron forces the peasants of a remote valley in the Alps to work themselves nearly to death. The devil in the form of a wild huntsman offers the desperate peasants his help, in exchange for a yet unborn unchristened child. The only person who is willing to strike such a pact is a farmer's wife (and originally a foreigner, adding a touch of xenophobia). The devil kisses her cheek; from this kiss grows an evil tumor in the form of a black spider. Twice, when the devil comes to collect a newborn, the local priest baptizes the child in the nick of time, but as punishment, the monstrous spider, now adult, births thousands of tiny spiders that start killing livestock and people, and finally breaks free from the face of the farmer's wife (who dies) and kills the priest and baby. The spider is finally sealed away when a brave mother, to protect her own newborn, grabs it and, dying, imprisons it in a hole in a wooden beam of her house, into which she hammers a peg to seal away the spider forever. Generations later, when people have stopped believing in the tale and become "sinful", a bragging servant pulls out the peg on a drunken bet and releases the devil spider, until it can again be sealed away by a pious woman who remembers the old tales and sacrifices her life for her child.
One of MR James’s favorite tropes was having an unpleasant being imprisoned in a tomb, grave, or ruin, inevitably later disturbed. Stories in this pattern include "Count Magnus" (the count's sarcophagus has three padlocks on it), "An Episode of Cathedral History", and "The Rose Garden".
The Damned, from Hells Children, by Andrew Boland, are sealed evil in a can, who spend the entire book trying to get out.
Cthulhu. Indeed, most Cosmic Horror uses a can of some sort to explain why the super-powerful beings haven't already destroyed humanity. In this case, however, nobody appears to have done the actual sealing or unsealing; the elder gods are just "sleeping", and will awaken "when the stars are right".
However, the Great Old Ones are not evil per se (save perhaps Nyarlathotep, and he is not always classed as one, and is properly an Outer God, ) but uncaring - they are simply far too powerful for us to matter to them, rather like a human stepping on ants (or for a better example, but purely Scots, the midge) and/or simply mindless - Azathoth for example, could (and apparently will) destroy everything, but he is blind, deaf, mute and completely unintelligent,and is no more evil than a hurricane.
Another example in Lovecraft's work is The Haunter of the Dark, an avatar of the god Nyarlatotep who is sealed inside the shining trapezohedron and can be summoned by gazing into it. Unlike the Great Old Ones, summoning him doesn't result in the end of the world, but he most likely wants some human sacrifices in exchange for secret knowledge or wants to possess you in order to get mankind to blow itself up.
The Silmarillion ends with the sealing of Evil OverlordMorgoth in the void beyond the boundaries of the world. He never escapes, though it is implied that Sauron was trying to find some way to release him during the Second Age.
Morgoth also spends 3,000 years in a can as punishment by the Valar. Eventually, because Good Cannot Comprehend Evil, they let him out for good behaviour, thinking he's repented. He hasn't.
Larry Niven's Known Space story World of Ptavvs has a scientific team releasing a Slaver, an ancient alien with large-scale mind control powers and an intense attitude problem, from the stasis field it has been trapped in for a billion years.
Fred Saberhagen's Empire of the East did this in an interesting way: the Demon-Prince Orcus, who founded the titular Empire, was imprisoned under the earth by his own lieutenants, John Ominor and Wood, in a coup. Eventually, Wood convinces Ominor that they should release Orcus, believing that only Orcus has the power to match Ardneh, and believing that they can keep Orcus controlled. They were right about the first point, barely. About the second, they were wrong. Also, Ardneh tricked them into releasing Orcus so that he could destroy Orcus and the Empire in a single stroke.
The blade Stormbringer in the Elric saga by Michael Moorcock straddles the border between this and Evil Weapon as it is both the form of an Eldritch Abomination that it takes on the mortal plane, and is the trap it is bound into. At the end of the saga, it finally breaks free as it is forced to consume a truly indestructible soul, Elric's, and is finally free to race through the universe, the last bit of Chaos left to supply growth and change in a universe of Law — supposedly this one.
Christopher Moore is a big fan of this trope, most notably in Practical Demonkeeping (Catch, the titular demon, is actually sealed away in a jar), Lamb Baltazaar keeps Catch, the same demon from the earlier novel, in a magically-sealed room which he tells Biff to stay away from. (Schmuck Bait) and You Suck.
Colin Wilson's The Space Vampires has a space mission to find a derelict ship drifting in the solar system. The astronauts board it and retrieve what they believe to be several human-like alien bodies. It turns out they're possessed by evil energy beings that live off the life energies of others. The very pulpy movie adaptation (called Lifeforce) has a similar initial situation, though it diverges pretty massively after that (the aliens turn their victims into zombies).
In The Chronicles of Thomas Covenant, the Creator sealed his Evil Counterpart Lord Foul the Despiser in The Land in order to keep the rest of the universe safe. Unfortunately, the Creator didn't really think it through very well, as Lord Foul can now wreak havoc within The Land freely, and if the Creator tries to interfere directly, it'll let Lord Foul out and destroy the Arch of Time (the universe).
In Who Censored Roger Rabbit?, it turns out that the titular murderer is a genie imprisoned in a Persian teapot that can only be released by a bonafide toon, who is sick of taking orders from self-centered people and starts deliberately spoiling the toons' wishes, until finally he just flat-out starts murdering them.
The initial premise of The Riftwar Cycle is that the God of Evil was imprisoned by the other surviving gods, but is now reaching out to influence things. Later books introduce successive complications, but those drift rapidly away from this trope.
The Black Company starts out with the can already having been opened but not all of the way in a bit of evil on evil backstabbery. Their employer was sealed away by the White Rose but then released by a group of sorcerers called the Resurrectionists. As thanks the Lady, a powerful sorceress who was sealed in there, kills them and then prevents her husband from getting out so she can keep the power to herself. He is not pleased and it's implied the world is doomed if he ever does get out. Once the Lady loses her powers and essentially switches sides against her former lieutenant, the Dominator is ultimately defeated and sealed in a silver spike, at which point is instantly reduced to ostensible Artifact of Doom and consummate MacGuffin that spawns a titular sequel chronicling the mad scramble to be the first wizard to obtain and unlock its secrets. Since the attempt to put the evil in a can inside another can that just happened to be the offspring of a Physical God was foiled miserably by a band of local scum, the Physical God drops it off in a Swirly Energy Thingy with assurances that the threat is vanquished forever, just like the even older Sealed Evil in a Can he himself guards.
In Deep Wizardry, the second Young Wizards novel, the seal on the Lone Power's can is weakening and needs to be recharged. However, what is sealed is only one aspect out of many that the Lone Power possesses, so It can be safely sealed away in one place while simultaneously being an active menace somewhere else.
Then in A Wizard's Holiday, the protagonists have to, among other things, open the seal and let the Lone Power out.
In the Dragonlance novels, and D&D campaign setting, Takhisis was essentially a sealed evil in a can from the end of the Third Dragonwar, when Huma Dragonbane forced her to swear to leave Krynn and never return, and the Cataclysm, when she found a way to get around that oath. In an interesting variation on this trope, it was when Berem stole the emerald from the pillar of Takhisis' temple, killing his sister Jasla in the process, that Takhisis was partially resealed.
She was actually able to get around her oath because of the Cataclysm — its precise wording was that she would never return "while the world was whole". With half the main continent blown up, the world was no longer whole so she was able to return. It's a bit of a stretch, but Takhisis is the Queen of Darkness.
In the series The Wheel of Time, the Dark One is making good progress in eroding the makeshift seal on the hole in the Creator-made prison that's kept it imprisoned for thousands of years. The hole was made back during what is known by the timeline of the books as the Age of Legends, although they did manage to patch it up again as best they could. Being as it is the God of Evil, existing outside reality, sealing and resealing really is the only option. During his resealing, his 13 highest-ranking disciples were sealed (mostly) outside of time as well, they ended up being freed first to pave the way for his return.
Stasis Boxes fit this trope when used for preserving the Gholams, not-quite-undead super assassins from the War of Power, beyond time and space.
How about Mierin's experiment in the Age of Legends that let the Dark One out in the first place? Even better because back then, nobody knew the Dark One existed, and her experiment was intended to tap a greater source of magical power able to be used by men and women (as opposed to the separate halfs of the one power). She later became Lanfear, one of the Forsaken, the most powerful servants of the dark one, though judging by a bit of Aiel ancestral memory that is tapped into, she was not evil to begin with, ie at the time of her experiment (as part of a team).
Mordeth/Mashadar is/are unable to leave Shadar Logoth after the fall of Aridhol (why is never really explained, but perhaps it was sealed intentionally). Mat Cauthon (or Padan Fain, or both) release it into the world at large after Mat removes the dagger. The can later is completely obliterated while cleansing sai'din.
The insane clone Dark Jedi Master Joruus C'baoth more or less sealed himself, ending up on the planet that The Emperor used as a personal museum/storehouse. C'baoth had no interest in the storehouse facility even after killing its guardian, and inhabitants of the planet had roughly feudal levels of technology. So he stayed there and ruled them, using his raw Force abilities and sort of mass mind-control to keep them cowed and obedient. Then Grand Admiral Thrawn showed up and recruited C'baoth with promises of new Force-sensitives to train and mold, both because C'baoth's Battle Meditation could allow great synchronization and increased efficiency in the fleet, and because he wanted the cloning technology in the facility. Thrawn's second in command really did not want to rely at all on someone so unreliable, but he was overruled. C'baoth's inevitable attempt at seizing power involved taking control of the entire Imperial fleet; when Thrawn talked him down and sent him back to that planet, C'baoth's next plan started with brainwashing an officer to the point where he had no will or mind anymore and died shortly after being taken away from the insane Master.
Another example of sorts in the same trilogy — an insane Bpfasshi Dark Jedi had been killed by Yoda on Dagobah, and his essence infused the tree where Luke had his pivotal vision during The Empire Strikes Back.
Another example from the Star Wars Expanded Universe: insane Eldritch Abomination Abeloth was sealed in a massive cluster of black holes, with a gravity-generating space station acting as a lock keeping her trapped there and unable to influence things on the physical place, and the Anthropomorphic Personification of the Light Side and the Dark Side of the Force doing an Enemy Mine every few thousand years to renew the lock whenever it started to break. This took the heroes over half a century to break; Anakin Skywalker killed the locksmiths, later protagonists broke the space station (they thought it was just a superweapon and didn't want it falling into the wrong hands), and then they used the black hole cluster where the ethereal monster was kept as a fortress. It still managed to keep her for about a decade.
Four hundred years before Galaxy of Fear, Ithorians tinkered with gene splicing and created something horrible. It took the Jedi to contain it. The Ithorians' Actual Pacifist beliefs make them averse to driving anything to extinction, so they isolated a sample and buried it in a tunnel in an asteroid. It was harmless sealed in a pod in the vacuum of space. Unfortunately they didn't bother with keeping a guard on it, so when someone Dug Too Deep...
Daniel Keys Moran's The Last Dancer has a scientific team releasing an ancient human, whose physical conditioning and skills approach Badass Normal from the other side and who has a major attitude problem (compare World of Ptavvs above). He proceeds to spend the rest of the book mainly kicking the otherBig Bad's ass, making him not so much Evil, just Sealed Badass In A Can.
Not truly evil, but definitely not good. In the Discworld novel Hogfather, Archchancellor Ridcully decides to unseal the door to a special bathtub invented by Bergoldt Stuttley "Bloody Stupid" Johnson, simply because it was barred shut. When asked why he wanted it opened, he replied, "To see why they wanted it shut, of course!" Terry Pratchett added the following footnote:
This exchange contains almost all you need to know about human civilization. At least, those bits of it that are not under the sea, fenced off or still smoking.
Pratchett also explores this theme in Reaper Man, where, in a time when Death is non-existant, Evil returns in the form of dinky little snow-globes that people want to love and cherish, since as you pick them up and shake them, snow appears to fall around models of city landmarks, and look, they'e even labelled A Present From Ankh-Morpork, how cool is that? But the globes are seeds of a potent and cruel ancestral evil that peys upon and kills cities....
Peter F. Hamilton does this in at least two series: in The Nights Dawn Trilogy Series, a wandering alien accidentally opens a portal to the afterlife, and in Pandora's Star and Judas Unchained, an alien menace is released by its hidden enemy (who has arranged a long-term "Let's You and Him Fight" situation between the menace and humanity).
Subverted in M. T. Anderson's book Thirsty, in which a group of vampires are trying to free the Sealed Evil, the god of vampires, and one character pretends to be trying to kill the vampire god in order to protect humanity, but in reality is assisting the god in committing suicide.
Also in the same volume, Tom Riddle's diary has the "memory" of the teenage Voldemort sealed inside, which Ginny unknowingly awakens through her liberal use of the diary.
In Harry Potter And The Deathly Hallows, it's implied that Voldemort's final fate is to remain in a sort of limbo (specifically, the netherworld where Harry met Dumbledore after he died) forever, incapable of harming anyone ever again.
In James Alan Gardner's Hunted, the Mandasars have queens who are very smart, very large, very strong, can persuade other Mandasars to do anything by emitting the right pheromones, and are physiologically hardwired so that each queen believes that she is the most competent person around and should be in charge. Having more than about four of them on the planet tends to mean endless power struggles; having that few risks having them all die. The solution implemented is to have a bunch of queens in cryonic storage. While they aren't evil per se, waking them all up at once is still really, really bad.
Quite a few of John Connolly's short stories involve Sealed Evil in a Can: the Daemon buried under the church in "Mr Pettinger's Daemon"; the Fairies trapped inside their fort in "The New Daughter"; the monster chained up at the bottom of the lake in "Deep Dark Green"; the nest of hibernating giant spiders in "The Wakeford Abyss"...
Also, in his novel The Black Angel, the fallen angel Immael is plunged into a vat of molten silver during the Back Story and the resulting statue becomes the angel's prison for several centuries. Naturally, the novel itself is all about Immael's twin brother and his followers attempting to free him.
In John C. Wright's Chronicles of Chaos, children being held hostage by Greek gods are nevertheless not sure that their own parents are entirely in the right; they find out, in due course, that they are hostage to prevent the forces of Chaos from moving against the universe and destroying it. They set up themselves to live safely and free in the universe until the gods could stand against the forces, without going home and so triggering such a war.
In Mistborn, Ruin, the primal force of chaos and destruction was imprisoned by his "good" counterpart Preservation after they teamed up to create life. This is a bit more complicated than most examples because Preservation split Ruin apart to make his release more difficult. Ruin's mind was put in the Well of Ascension, while the bulk of his power was bound into the atium. The problem was, even an imprisoned Ruin still had some power, so he altered the prophecies regarding a messianic figure called the Hero of Ages to say that the Hero should go to the Well of Ascension and release its power to the being trapped there. Following the prophecy, the heroine of the trilogy does this. Oops.
Gonko: You come get your chuckles whenever you're ready, 'cause if they ain't lettin' me go, they ain't lettin' you go. Best believe that. Show's down but not out, mark my words. We'll be back in town, my pretty, and I don't recall offering you a severance package.
While not a single character, the Mijaki were confined to the borders of their lands in Karen Miller's Godspeaker Trilogy because they made the world evil. Hekat then decides to change things.
In the Stephen King novel Duma Key, the villain, Perse, is an evil doll/creature who is sealed in a keg which was dropped down a well. Unfortunately, the keg had been leaking for some time and by the time the main character finds it, it's almost empty. He eventually ends up sealing Perse in a flashlight filled with water (her weakness) and eventually creates a tight, silver container to hold that it and throws it into a lake.
Another king example is the short story "The Crate", later adapted as one of the segments of Creepshow, where a crate containing a terrible monster is opened by a janitor.
The T'lan Imass of the Malazan Book of the Fallen are notable offenders for this. During their genocidal war against the Jaghut and, off-and-on, the Forkrul Assail, they developed a ritual for binding enemies when they lacked the strength to directly kill them. Either pinned under massive stone slabs or buried in barrows, it's not uncommon for their ancient enemies to be unearthed.
The Azath House seals away both good and evil, trapping them until such a time as they are needed in the world or the Azath dies.
It's not entirely clear who was doing the sealing, but there have also been cases of bound K'Chain Che'Malle who predate even the T'lan Imass.
Wyrm, the enormous, snakelike Eldritch Abomination that is the main villain of The Book Of The Dun Cow, was sealed inside the earth during the creation of the world to stop him from destroying the universe. The aim of the main characters is to prevent his escape.
In Memory, Sorrow, and Thorn, the Big Bad, Ineluki, is a Sithi sorcerer who went mad trying to protect his people from the onslaught of mankind. He cast a forbidden spell in an attempt to destroy the conquering army, but killed himself instead. Even in death, however, his hatred burned so strongly that his spirit refused to leave the world, lingering instead in the realms beyond death for five hundred years, until the circumstances become right for him to be freed via a complex ritual involving Demonic Possession. It is stated outright that if he succeeds he will destroy all living things in his longing for Unbeing.
In "The Wizards Are Dying", the godling lich Xanthak is released from imprisonment when a group of adventurers takes a jeweled cross called the Nga from the door that seals his cell. Another group of adventurers has to put him back in his cell and seal it again.
"Out of the Eons", one of Gardner F. Fox's "Niall of the Far Travels" short stories. Adonair is an evil deity from another universe trapped in a brick-lined cubicle eons ago by the deities of Niall's universe. During the course of the story Niall accidentally releases him and he and the gods must find a way to destroy him.
Alex Verus encounters two of these. One is a magician who sealed himself in an artifact. The other is a magician who is trying to live forever by killing others like the long dead vampires.
In the late James Herbert's novel The Fog (unrelated to the John Carpenter film of the same name), an earthquake ruptures a buried canister, releasing an insubstantial, misty organism called a mycoplasm. Otherwise respectable people do decidedly hideous things when they come into contact with it.
Rita Repulsa from the first season of Mighty Morphin' Power Rangers was originally trapped in a "space dumpster" on the moon (or a moon, or something) for 10,000 years until astronauts accidentally released her. Her line from the intro sequence is rather iconic:
Ahh! After 10,000 years I'm free! It's time to conquer Earth!
Incidentally, Rita Repulsa's counterpart in Kyoryu Sentai Zyuranger is called Bandora the Witch, a reference to Pandora.
To a lesser extent, in the episode "Final Face-Off," Rita opens an urn which imprisoned the legendary Face Stealer. The Rangers lock him back in the urn upon his defeat at the end of the episode.
Power Rangers Lightspeed Rescue's villains are released from the "Tomb of Forever" by an unwitting Egyptologist. The villains then go about trying to free their still-sealed Queen. They all more or less end up that way again in the finale when they are either destroyed (sending their spirits back) or by physically being thrown back into the "Tomb of Forever", sealing them in the Shadow World.
While not applying to the main villains of Power Rangers Time Force, the individual monsters fit this trope, being mutant prisoners shrunk, cryogenically frozen, and sealed inside small containers. They also return that way when defeated.
The Orgs of Power Rangers Wild Force were spirits sealed in the earth 3,000 years ago. They were freed in the present day to possess everyday objects due to pollution and the appearance of a successor to their Big Bad.
Power Rangers Ninja Storm has the "Abyss of Evil" that acts as one. Unusually, the Big Bad didn't bust out of there at the beginning of the season; instead it factored into his Evil Plan: if his monsters couldn't defeat the Rangers, they'd be sent to the Abyss; cramming it full until it burst open and gave him an army to work with.
In Power Rangers SPD most of the individual monsters and main villains fit this trope, being alien criminals. They are trapped inside special cards when defeated.
Rita Repulsa's very line is echoed by the Wolf Knight's first line in Power Rangers Mystic Force (He actually says "After all these years, I'm free," but the similarity was close enough that many fans were confused into thinking the backstory was set ten thousand years previous, when it actually appears to have been more like 20).
In Power Rangers Operation Overdrive all four big bad factions has someone sealed inside a different can. Moltor and Flurious were sealed inside two lifeless planets, one of extreme heat and the other of extreme cold respectively, when they tried to grab the season's MacGuffin, and freed when said MacGuffin was discovered on Earth. Kamdor is initially sealed in a blue gem necklace until he is freed with a stolen device by his partner Miratrix, who incidentally later becomes sealed in same said necklace when Kamdor double crosses her. Then there is the "Prison Mirror" which contains an army of Fearcats, but was destroyed with only Benglo escaping. In another episode, Thrax, the son of Rita and Zedd, repeats the same line his mother made when released from a Space Dumpster, after what could not have been more than two or three years.
Power Rangers Jungle Fury has Dai Shi, who has been stuck in an (unlocked!) box for 10,000 years. The box was kept by a secret order, but opened when a disgruntled student barged in and attacked the order's master, knocking the box out of his hands. Unusually, however, Dai Shi is significantly weaker than he was, and has to struggle to regain his powers before the Rangers become strong enough to destroy him.
Dai Shi's "seal" makes a "Funny Aneurysm" Moment out of Juken Sentai Gekiranger'sending. The main bad guy, whose final form is the basis for Dai Shi's true form, proves to actually back up his claims of indestructibility. As the truly immmortal "Infinite Dragon," he will simply return no matter how thoroughly blownuptified he is. So the Gekirangers wind up sealing him in a can, and then not being sure what to do with the can afterwards, though it's said that breaking the sealing spell isn't as easy as... say, using him as a pool ball. Jan, whatever you decide to do with him in the end, please for the love of God invest in a lock.
This season also had other sealed cans. The Crystal Eyes for the Phantom Beasts, The Overlords lifeless bodies/shells & two of the "5 Fingers of Poison" urns with broken remains (both revived by Naja's life talons), the various statue soldiers brought to life as monsters of the day, and the Spirit World (at the finale) which acted as both a sealed can of evil (for Dai Shi's fallen minions) and a sealed can of good (for the fallen Masters).
Venjix from Power Rangers RPM began its existence more or less as a sealed evil. The program for the sentient, self-replicating, computer virus was initially created and contained in a single laptop. That is until Dr. K, in a attempt to escape her circumstances, decided to infect Alphabet Soup's computer network with the virus but was stopped short from installing a firewall to prevent further spread. The result was an infection of nearly every computer system connected to the internet and the destruction of nearly the entire human race.
It is hinted that Venjix also becomes one of these again, as opposed to being destroyed, at the end of RPM with the Venjix Palace music playing as the camera focuses in on Ranger Red's morpher with a blinking red light.
The Sanzu River from Power Rangers Samurai and Samurai Sentai Shinkenger is one to the Master Xandred/Chimatsuri Dokoku and the Nighloks/Gedoushu, as nobody (especially Xandred/Dokoku) can last long away from the river before they dry out. Only a monster and some Mooks are able to go out at a time, trying to increase peoples' despair and sorrow in order to make the Sanzu's water level rise until it seeps into and floods the human world.
Khan Noonien Singh and his cryogenically frozen followers, in the TOS episode "Space Seed". And again in Star Trek II: The Wrath of Khan, when he's abandoned on Ceti Alpha V (which the crew of the Reliant mistake for Ceti Alpha VI after a natural disaster alters its orbit and destroys its environment).
In the classic series episode "The Alternative Factor", if Lazarus and his insane counterpart from the antimatter dimension were ever to meet in the same universe, that universe would be destroyed. Both of them are sent into an intermediate dimension so that this can never happen, and where the two of them will be locked in combat for all eternity.
"God" in Star Trek V. He claimed to have been imprisoned on the planet in the center of the galaxy and wanted to "join" with the Enterprise so he could escape.
Data's evil "brother" Lore. He's found disassembled in Dr. Soong's lab and the Enterprise crew make the mistake of putting him back together.
Well, in the animated version episode "Beyond the Farthest Star", Kirk tricked an ancient evil entity onto a black dwarf star, where it moans about how lonely it is as the credits roll.
This was supposedly the plot behind the Star Trek: Voyager episode "Dragon's Teeth", when Seven of Nine releases an alien race from a 900-year stasis... only for them to turn out to be your bog-standard Villains of the Week piloting obsolete spaceships. Disappointing.
Another episode played off the Real Life example (see below) of nuclear waste- Data is injured while retrieving said material from a crashed Starfleet ship, and after the ensuing memory loss he stumbles into a local village. His radioactive-shielded briefcase doesn't stay closed for long.
Many, many examples in Buffy the Vampire Slayer (the Judge, Acathla, others) and Angel (Illyria, Pavayne,Sahjhan). In fact, the Angel example showed us a veritable warehouse of sealed demon gods like Illyria, which (as of the end of the series) is left unguarded.
There is also a very literal variant in the Buffy episode "Get It Done", when The Shadow Men try to infuse Buffy with the essence of a demon that they kept sealed in a box.
Katherine and two dozen other vampires in The Vampire Diaries were sealed in a tomb beneath the town church. In a slight subversion of the usual formula, this was actually an attempt to SAVE Katherine from the town's vampire hunters.
Actually it was Katherine's plot to kill the tomb vampires because they knew she was alive and eventually word will get back to Klaus and he would find and kill her for his sacrifice. So she plotted with George Lockwood in 1864 to have them take the blame for the killings George was doing. George was a werewolf and he was killing all those people. So their interest met: The tomb vampires would take the blame for George's killings and at the same time be eliminated to keep Katherine's secret from Klaus. Katherine's "payment" for this was the moonstone George had.
The dagger dipped in white oak ash only kills the Original vampires if it stays in place. Klaus keeps all his siblings in coffins with daggers in them. He wakes up Rebekah when he needs her necklace.
Mikael. Katherine wakes him up, but no-one except Damon and Stefan is aware of this yet.
Esther, the Originals' mother who initially turned them all into vampires. Klaus tore her heart out and has been keeping her in a coffin, thanks to a spell that preserved her body perfectly.
Despite the frequent use of the "Pandora's box" analogy, it was really Earth that was sealed in a can at the beginning of Stargate SG-1. On the other hand, there are several examples of villains being effectively sealed in cans, such as Osiris (who was in a canopic jar), Anubis' son (in a stasis chamber), the Wraith (hibernating), and the Ori (in a distant galaxy blissfully unaware that free humans existed).
One of the most literal Stargate SG-1 examples would be Hathor, who had been sealed in her sarcophagus for 4,000 years, only for some unwitting archaeologist to open it.
As well as Marduk. He was so bad by even Goa'uld standards that his servants locked him in a sarcophagus with a ravenous predatory beast. As it continually ate him, the sarcophagus' nigh-magical healing powers would keep healing him and see to it that it took him centuries to die. Damn. However, the Goa'uld are Puppeteer Parasite, so Marduk simply pulled a body-switch and took over the predator. And then Our Heroes go poking around in there...
The Replicators were sealed in a can by the Asgard, but it gets worse when the Replicators outwit the trap and crank it Up to Eleven before SG-1 arrive to fix the can.
One episode of Highlander: The Series featured a Nazi Immortal who had been chained and thrown into a river by a young boy. How do you make a Nazi cross? Forty years of drowning and reviving every few minutes ought to do it...
There is at least one story of an Immortal being on a sunken ship and having to walk back — Kit O'Brady was on a boat to Alaska when it sank, and said it took him months to walk back.
And then there's the example of the Immortal stranded on a deserted island for years, dying of starvation and thirst every so often, just to wake up and do it again. For some reason he held a grudge...
In the Doctor Who episode "The Satan Pit", a being known only as "the Beast" (who claims to be Satan) is revealed to be at the core of a planet perilously held inside of a black hole's event horizon. Any attempt to escape would wreck the system that kept the planet out of the black hole's gravity, thus sucking it and the Beast into the black hole.
The original series used this trope often. Sutekh The Destroyer in "Pyramids of Mars", Omega in "The Three Doctors" and "Arc of Infinity", the Ice Warriors, the mutagen under the Earth crust in "Inferno", the Krynoid pods in "The Seeds of Doom", and many more.
A slight variation happened in "The Stones of Blood", where the Doctor releases a pair of biomechanical judges from a ship stranded in hyperspace, and the judges promptly sentence him to death for letting them free without the proper legal authorization.
"Doomsday" features the Genesis Ark: a Time Lord device imprisoning millions of Daleks. "Time Lord science: it's Bigger on the Inside."
In the new series episode "The Runaway Bride," it is revealed that the centre of the Earth contains hundreds — possibly thousands — of omnivorous intelligent alien spiders. Indeed, the vessel that holds them is the original core of the planet, nearly five billion years old.
In the episode "The Pandorica Opens", the Doctor investigates the eponymous Pandorica, which is advertised as containing the most feared being in the universe and is starting to open. It's empty. The Pandorica was created by a coalition of the Doctor's enemies to trap him inside, because they believe he will destroy the universe, and it's opening so that they can put him in — due to time-travel, he has arrived before the myth started. The Doctor is predictably fascinated; "What could be so dangerous?" he wonders. You.
In "The Waters of Mars", Humans accidentally released Sealed Evil in a Glacier.
Then there is the Old God in a Pyramid in The Rings of Akhaten. It turns out the real Monster is the Sun.
The first Torchwood season finale features Abaddon, son of The Beast who was sealed within the Cardiff Rift.
In Season 3, in a slight subversion, daddy Petrelli appeared to be far more powerful than Adam and took his power, killing him instantly.
Arthur Petrelli himself has elements of this, starting off the series on life support and only able to communicate through telepathy.
As of Volume 4's finale Sylar's brainwashing into believing himself to be Nathan Petrelli certainly qualifies. It didn't last.
Volume 5 has Sylar being imprisoned inside his own head and Parkman sealing his comatose body inside a brick cell.
In The Twilight Zone TOS episode "The Howling Man," the evil sealed in a cell was the Devil himself.
In Babylon 5, the Shadows were something like this, except that they weren't sealed by other people. They regularly hibernate and wake themselves up.
The Thirdspace aliens are effectively sealed until their gateway is opened.
Also The Hand. (Who are probably the Thirdspace aliens anyway.)
One episode from Los Luchadores dealt with a plot to awaken a demon in a ritual involving three descendants of the people responsible for originally sealing it. In this case, the ritual is successfully interrupted just before its completion, denying the audience the spectacle of watching an ancient evil being defeated by a masked professional wrestler.
In the original and revived Dark Shadows, vampire Barnabas Collins made his series debut when he was released from the chained-up coffin in which his father, unable to go through with staking his own son, had sealed him.
Supernatural has used so many variants of this it's the only kind of Myth Arc they've ever had, but at least it always varies: Devil's Gate was opened with no warning and a bunch of stuff got out along with the actual new Big Bad; Lucifer was freed by Thanatos Gambit; the Leviathan were the real problem with opening Purgatory since Cas managed not to blow up the universe, but Death didn't have the decency to warn the characters about them...
Azazel's goal in the season 2 finale was to open a Devil's Gate in Wyoming in order to release Lilith and a demon army into the human world. Lilith would be needed to later break Lucifer out of his cage.
In season 6, we have Purgatory, the place that creatures who don't belong in either Heaven or Hell go when they die. This seems to make it a repository of monster souls; it also contains a being known as the "Mother of All" which they call Eve, probably because they already used the names Lilith and Tiamat for other purposes, and apparently some very nasty formless things that were never alive in the normal sense. Cas and Crowley work together to open it in order to use the monster souls as a power source, but there are side effects.
And then the first episode of the seventh season reveals that Purgatory was originally created to seal away the Leviathans, beasts that God feared would (as Death put it) "wipe out the rest of the petri dish".
To put it simply, thus far the end of every even-numbered season has involved letting some great evil out of its can. Seasons three, five, and seven have been about dealing with these evils (which are, in order, a plague of demons led by Lilith, then Lucifer, then the Leviathans. Evil in this show also tends to start with L.)
In LOST, Jacob claims that this is the role of the Island. It is implied that the Man in Black/the Smoke Monster is the evil being imprisoned.
In Lexx, Kia is an assassin who spends most of his time frozen so he's save his protoblood for when he's needed, which is only when someone needs to be killed.
In Kamen Rider Kuuga, the Grongi were imprisoned in a tomb by the original Kuuga after he defeated them.
In Kamen Rider Agito, the Overlord of Darkness has a somewhat odd version of this, he was already dead, but left his DNA around, allowing him to retake his physical form when humans uncover it
Kamen Rider Blade has the Undead, who have been imprisoned since the beginning of time, after serving their purpose and deciding the dominate species of life on Earth. Though since not all of them are evil, some would be Sealed Good in a Can and since most of them just want to fight one another, they would be Sealed Badass in a Can. The Roaches and Black Joker defiently fit the trope though. There's also Jashin 14 in The Movie.
In the newest series, Kamen Rider OOO, the Greeed have been imprisoned in a stone box for 800 years until they're released during a robbery. The stone box? The original OOO.
In Fringe, the pieces of the First People's Machine, which has the power to create or destroy universes, were scattered all across the globe and buried hundreds of feet underground.
Clark manages to escape on his own, without help from the outside, and subsequently reimprisons Zod in the season six premiere. He then spends the rest of season six hunting down the other Phantom Zone prisoners who escaped at the same time he did one by one and either killing or preferably reimprisoning them.
In Forever Knight, LaCroix's daughter was sealed inside a coffin after LaCroix staked her. The Egyptian sun disk kept her prisoner much like a Christian cross, until she was released by grave robbers and came after him and his children.
Also pops up in the first Forever Knight novel, "A Stirring of Dust".
In Tracker, Zin gets sealed in an underground vault during his attempt to steal the alien weapon hidden there.
Merlin and the goblin, who was sealed in a box, then escaped to torment everyone in the castle, and then resealed after being trapped by Merlin and Gwen.
It's debatable whether Peter Kramer was evil per say or just driven crazy by the Drake, but in any case, his spirit was locked inside a suitcase, which was then locked in a storage room in the basement that was bricked shut.
In MythQuest, Gorgos was shut away inside a stone for trying to change the myths of humanity. Matt Bellows accidentally releases him in the first episode, but only into a slightly bigger can. With significant air holes.
Every Bal Sagoth song starts with "Oh shit, we just woke up Cthulhu." This is all the more impressive considering that (actually) awakening an elder god would crush the mind of anyone near it, then plunge the Earth into a never ending night.
"Bark at the Moon" by Ozzy Osbourne is about a beast that once terrorized a town, but was eventually buried in a nameless grave. And then he ends up returning to cause some more destruction.
Just saw this in the opening of an article about the third Guitar Hero game:
"As is the case with all ancient evils, 80's rock music was never sealed away in a very permanent fashion."
The Titans were locked inside Tartarus, a dank, gloomy prison "as far beneath Hades as heaven is high above the Earth", where they were guarded by their siblings the Hecatonchires.
Typhon was trapped beneath a mountain by Zeus.
Norse Mythology: Unbreakable magic chains kept Fenrir (a gigantic wolf so massive that is must crouch down to avoid scraping against the dome of the sky) bound, until he eventually breaks them. Ironically, it is implied that binding him is what made him so pissed off at the Gods in the first place. (Well, that's the trouble with prophecies... and he is a child of Loki, God of betrayal, mischief, and "evil".
Ragnarök could be best be described as every Can in Norse Mythology opening at once. Everything broke free. Jormungandr, Fenri, Loki, the forces of Hel, Garm, etc.
The legends of genies often fall under this trope. Not all genies are good, ya see, and the good ones will interpret wishes literally.
Moreover, the Ur Example for many of the bad jinn/wicked ifrit stories is the tale that Solomon/Sulayman used his ring to seal (yes seal, with molten lead and a magic seal ring) a number of bad jinn into brazen urns (which is a fancy name for brass cans) and cast them into the ocean, only to have them later dredged up as in stories like "The Fisherman and the Genie." Since this has an evil spirit sealed in an actual can, this makes this trope 'Older Than Feudalism.'
According to Islam, Dhu'l-Qarnayn, or "He of the Two Horns" (a lesser prophet who appeared long before Muhammad) encountered a race of monsters (split into two tribes, the Yahjuj and Mahjuj, or Gog and Magog of Biblical fame) that were harassing the people, so he built a giant wall to keep them enclosed. They won't be able to escape until Allah says so, which will be during the lead-up to Yawm al-Qiyāmah (the Day of Judgment).
In 4th Edition, the entire plane of Baator is like this, being created by a divine curse to imprison the Magnificent Bastard Asmodeus and the devils. Unfortunately, said can is rather flimsy, and while it does a good job of holding Asmodeus, any infernalist worth his salt can create a temporary portal to it, allowing the devils to stream through and wreak havoc and contracts.
The seal wasn't made to save mortals from Asmodeus and his devils — but to save the other gods from him. Hence why mortals are free to poke holes at the seal and let devils come and do Faustian pacts. If you are dumb enough to do it, you deserve what's coming to you.
You have grasped the entire concept wonderfully. Asmodeus will be pleased.
One example is the Homebrewed class, The Harrowed. Anyone with this class is this for their own unique destructive being that they call 'the monster within' which is constantly raging to get free from its host. Ironically if the beast were to be released it would be promptly obliterated by about seven different gods at once, this won't ever happen though because plenty of greater deities have been left scratching their heads after failing to remove the beasts. This class cannot even use any of their abilities without provoking the beast and needing to make a will save or let it gain control for a few rounds of combat.
If you think that the Harrowed are justified in wanting to die, they aren't. They are stuck in a constant cycle of reincarnation after they die and they always come back as another Harrowed with exactly the same homicidal beast sealed inside them. They are such a tight can that not even death or the gods can crack them open.
In the Back Story the current gods sealed the evil gods that ruled before them, each in a different way befitting them and tailored so that their powers couldn't get them out. This editor's personal favorite: Thulkas, the Iron Lord, was so strong that he couldn't be moved, so he was hammered into an arrow and shot into the sun.
The Scarred Lands also has the Slarecians, psionic beings who challenged both the gods and the titans. The twist is is that they sealed themselves into the can so they wouldn't be destroyed.
In the published version of B3: Palace of the Silver Princess, a huge ruby called My Lady's Heart turns out to be a Canopener for an evil Immortal, Arik. Even the leakage of Arik's power which the gem emits is enough to petrify a royal court, trap its best defenders in a dimensional prison, and attract monsters and fanatical dark priests from hundreds of miles around.
An important part of Eberron is that there are multiple Sealed Evils in various Cans, with sealants as strong as the plot demands of them.
The massive Ptolus setting by Monte Cook is set on the world of Praemal, which exists as a giant can in which to seal evil. The city of Ptolus itself is built on top of a can or ten and has a giant, impossibly high spire in it where a cleric once, long ago, tried to seal all the evils of the world in a can. Then he became evil, and eventually his fortress atop the spire was itself sealed with the remains of his work (and his remains) within it. It's a pretty can-heavy setting.
Another notable example in the Points Of Light setting is Torog, god of torture and imprisonment. The kicker? The earth is his can. He's trapped in the underdark, actively crawling around down there, and occasionally reaches up from below the earth to pull whole cities down into his can with him.
In the Greyhawk setting: Zuggtmoy (in the Temple of Elemental Evil), Iuz and Fraz-Urb-Iuu (in Castle Greyhawk) and Tharizdun (in his Forgotten Temple).
In the Midnight setting there is the evil god Izrador, who was sealed (along with some other beings) in the world of Aryth. The bad part ? Your characters live on Aryth and they're also sealed there. Not only is the evil in the can but you're in the can with it. Crapsack World indeed.
In the Forgotten Realms setting: one of the oldest cans would be the Sharn Wall, erected by the creatures which gave it its name so as to keep the phaerimms sealed away from Faerűn. Weakened severely over the millennia, it is later brought down by the return of the Shadovar, who then must team up with the Sharn and the peoples of Toril to drive the phaerimm back. Other examples include: the djinn Calim and the efreet Memnon, locked in eternal struggle forever, their battle creating the Calimshan Desert; Sarya Dlardrageth and the rest of her fallen house of demon-interbred Elves, trapped in the Nameless Dungeon beneath Hellgate Keep, who are inadvertently freed when the Mistmaster and his Harper allies destroy Ascalhorn's mythal with the Gatekeeper's crystal; Iyachtu Xvim, son (and receptacle) of Bane, imprisoned beneath Zhentil Keep until he breaks free in the wake of Fzoul Chembryl's reading of The True Life of Cyric; an illithid and a rakshasa that became trapped in stasis beneath Beorunna's Well after seeking revenge on Runlatha for their previous imprisonment and torture and who are even now (by using an image of the rakshasa to pretend to be the totem spirit of the Red Tiger Clan) trying to obtain the cooperation of the Uthgardt barbarians in securing their freedom; and the three nycaloths accidentally freed from their dimensional pocket by the flight of "a red dragonthat never held malice or greed in its heart over the coronal's throne"—which leads directly to the Weeping War and the fall of Myth Drannor.
The artifact known as the Acorn of Wo Mai holds an evil demigod called the Copper Tyrant of Tros that will try to trick anyone possessing the Acorn into letting it loose.
Daemon weapons contain bound daemons within them, giving them incredible power and just as incredible malevolence. However, the greatest threat isn't them escaping, but rather corrupting the weapon's wielder and twisting them to its will.
More powerful daemons, who couldn't at the time be banished back to the Warp, are often sealed in the Materium in some way that prevents them from killyfying everything at the moment, perhaps in the hope that they can be banished later. This being WH40K, not only does the sealing frequently make things worse, but most of the time those doing the sealing never tell anyone about it.
Both literal and metaphorical in the case of the Necrons and their C'tan masters, who sealed themselves deep beneath the surface of numerous worlds approximately sixty million years ago.
In the prehistory of Exalted, the defeated Primordials were stitched into the twisted body of their god-king Malfeas and confined to another realm... mainly because the Exalted looked upon the Primordials who had been killed, seen that they'd brought the Underworld into existence, and said, "Yeah, that ain't supposed to happen."
There are also the Neverborn, the aforementioned Primordials that had been killed. Being too big to die properly, they instead wrapped themselves up in giant sarcophagi spanning infinite distances as they resisted the pull of Oblivion. Then the Solars decided to pop a few blocks open to learn Necromancy...
From the perspective of the Bronze Faction, this was the case for the Solar Exaltations locked in the Jade Prison for ~2000 years.
Scion, by the same company, uses the same logic surrounding the Titans. At the end of the Titanomachy, the gods bound them away in the various Underworlds — this was because the Titans were incarnations of things such as Light, Fire, Darkness, Life, and Water, and their death would screw with reality big time. This was proven when Ymir was killed... causing the Great Flood, as the Ice Age ended right then and there.
Champions adventure The Blood and Dr. McQuark. Azor (an agent of some Eldritch Abominations) was imprisoned by the Council of Nine but escapes during the course of the adventure.
In the game Neuroshima there is a number of items scattered around the world, which adventurers refer to as Pandora's boxes. Each is a large metal canister that contains something nasty (from biological weapon to a very compact assassin droid). Everyone knows what they are but humans being humans, every once in a while someone opens one, either because of the Schmuck Bait involved or in some desperate gambit against his enemies.
In Iron Kingdoms the Skorne have Ancestral Guardians, which are statues empowered by the souls of fallen Skorne warriors.
In the In Nomine universe, one of the prophecies for Armageddon is "An ancient evil breaks its bonds." One of the possibilities for fulfilling this is Magog, Demon Prince of Cruelty, who was sealed in an ancient Egyptian tomb exactly one day after falling from Heaven.
BIONICLE: Makuta Teridax encased in a Toa Seal by the Toa Metru by their Elemental Powers, but much later they unintentionally released him with the same powers when they attacked Roodaka holding a piece of the Toa Seal.
Dawn Of War, the original one, has an absolutely beautiful example. An ancient demon imprisoned in a stone manipulates Orks into attacking human cities on the planet. Space Marines come to the rescue and do what Space marines do best - spill ungodly amounts of Orkish and human blood - just so at the end, the demon can reveal that the entire planet had previously been converted into a blood altar for releasing him. Bonus points: most characters wanting to use demon or its power for their own end up badly.
The Chaos Rising expansion to Dawn of War II also features a plot to unseal a demon trapped inside a planet that was lost in the Warp.
In Dark Messiah Of Might And Magic the Demon lord is locked in a prison under the city of Stonehelm, however the original prison is flawed and can be broken, the player can choose to get the good ending and seal him away forever by repairing the seal or get the bad ending by releasing him.
In the first Avernum / Exile game, there is the Haakai Lord Grah-Hoth, who was sealed in a bottle before the game begins. Despite being unable to directly act, the game reveals him to be manipulating events, such as aiding the Slith against the humans who imprisoned him.
Ziria has the Daimon Cult trying to revive Masakado.
Manjimaru has the Root Clan trying to revive Yomi.
Fuun Kabuki Den has the Daimon Cult trying to revive Garp.
Fourth Apocalpyse has the Dark Society trying to revive their Absolute God.
In Tomb Raider and the remake, Tomb Raider Anniversary, Natla was locked in limbo for thousands of years after using her powers for evil.
In Okage: Shadow King, King Stan has been (purportedly) stuck in a bottle for the last 300 years, waiting for someone wimpy enough to let them possess his shadow. Additionally, while he was stuck in the bottle, a number of monsters stole portions of his evil power and became "Fake Evil Kings". He then drags the main character around to defeat them and get his powers back so he can take over the world.
In Rune Factory 2, mysterious earthquakes start happening about a third of the way into the game. Eventually, the character's child finds these are being caused by a Sealed Evil in a Can which is about to escape and destroy the world.
And there was also Bongo Bongo, the Evil Shadow Spirit from ''Ocarina of Time' that was sealed in the Bottom of the Well.
The Legend of Zelda: Spirit Tracks features demon king Malladus, who tyranized the land that would one day become New-Hyrule when Tetra and Link arrived. He was sealed by the ancient Lokomo spirits underneath vast chains that eventually developed into a railway-system.
In The Legend of Zelda: Skyward Sword, the God of Evil Demise was sealed by the goddess Hylia. His servant Ghirahim who is actually Demise's sword seeks to free him and succeeds. In the end, Link seals away Demise again within the newly forged Master Sword.
In Evil Zone, the inhabitants of an island dimension sealed away an incarnation of a cosmic destroyer, but couldn't finish the job themselves, so they had to hire out heroes to finish the Big Bad off.
In Dark Cloud, the general of an expansionist empire frees the Dark Genie from its place of captivity. At first, it seems to grant his wish by destroying every other nation on the face of the planet, but in the end, it takes over his body to progress towards its final goal — the complete destruction of everything.
The Dark One of SRMTHFG has nothing on the Profound Darkness in Phantasy Star IV; the Precursors sealed it with a solar system.
In the Diablo series, when the Prime Evils were unleashed upon Sanctuary, the Archangel Tyrael selected a group of mortals known as the Horadrim and charged them with imprisoning their essences into the Soulstones so that they would not be reborn into the Hells upon death. But thanks to the betrayal of Tyrael's lieutenant Izual, who filled the Prime Evils in on the Soulstones and how to corrupt them, it turns out that this played directly into their hands.
Illidan Stormrage in Warcraft III, another Blizzard production, is imprisoned in a cage for 10,000 years for continuing to research arcane magic after the night elves had banned its use. Also a subversion in that Illidan is not evil at the time of his imprisonment, but has become obsessed with power and revenge by the time he is freed.
In a continuation of this universe, a majority of raid bosses in World of Warcraft are sealed evils. The quests to kill them generally go something like Go beat up these mildly bad dudes who have this Big Ancient Evil imprisoned, so that you can kill him too. One wonders why the player doesn't just say But, they're doing a fine job keeping him imprisoned! What happens if I manage to kill them but the Big Ancient Evil kills me? A variation goes Go beat up these mildly bad dudes who are trying to unseal this Big Ancient Evil before they succeed, then kill the half-unsealed form of the Big Ancient Evil, which makes a little more sense.
Warcraft's universe also has the Old Gods, very similar to Lovecraft's Great Old Ones, sealed beneath the world and waiting to be freed. For the longest time, it was a total mystery why the god-esque Titans didn't just kill them all, considering they'd managed to off one. Recently it was revealed that the Old Gods are parasites who have bonded with the planet of Azeroth so that killing them will cause untold damage to it. And yet, the players continue killing them for loot...
The fourth expansion to World of Warcraft (Cataclysm) involves the unleashing of Deathwing, the Earth Dragon who was slowly driven insane by the Old Gods and imprisoned in Deepholme, the elemental plane of earth. His emergence not only blows up parts of the world, but also opens up the elemental planes, which are full of Sealed Evil in a Can, including the elementals themselves (locked up because they were tearing the world apart with their wars)
Maybe Illidan wasn't evil, but he did kill people with a handwave who tried to stop him from corrupting a lake with the Well's water.
The Mists of Pandaria expansion features the sha - beings of pure hatred and other negative emotions - as this. It later emerges that [[an artifact called the Divine Bell has the ability to control the sha, and Horde Warchief Garrosh Hellscream orders it stolen in an attempt to make super-soldiers with it. It misfires when the sha ends up controlling its test subjects instead of the other way round, and have to be slaughtered by adventurers]].
Coincidentally, Homeworld: Cataclysm also involves a similar scenario. Somewhere around a million years ago, the extragalactic exploration vessel Naggarok picked up a deadly technoorganic entity in hyperspace. Seeing no way to defeat it, the crew scuttled the engines, trapping the entity in deep space. However, they screwed up as the ship auto-launched az empty lifepod with a transmitter (and some Beast material) onboard. In the present, the Kiith Somtaaw mining ship Kuun-Lan finds the pod and opens it. Cue to a race with time to find both the Naggarok and the new Beast mothership and blow both to smithereens before the whole galaxy suffers a fate worse than death (ship crews aren't simply killed, they're broken down into biomass to function as a makeshift neural interface between ships and the Beast - and judging by the sound of it, it's not exactly painless).
Bentusi: We will NOT be bound!
The main storyline of The Elder Scrolls III Morrowind focuses around preventing Dagoth Ur, a godlike being imprisoned for 3500 years, from fully regaining his sealed powers.(though he wasn't imprisoned but passed out)
Likewise, in its followup, Oblivion, the player must prevent Mehrunes Dagon, lord of the titular realm, from unleashing his forces upon the world. Dagon isn't really sealed IN anything so much as he is kept OUT. In this case, the world is the Can Sealed Against Evil.
In The Elder Scrolls V Skyrim, the Sealed Evil in a Can is Alduin. And he isn't unsealed by someone playing around with something they know nothing about, but was an inevitability since his sealing involved him being cast adrift outside of time. A prophecy describes the events that must transpire before he would end up back in linear time again.
Dracula's castle in the Castlevania series is eventually sealed this way after the Dark Lord's death. It's sealed inside the total solar eclipse of 1999. In the solar eclipse of 2035, it sucks in everyone present at the shrine where the sealing took place.
Dracula, and Castlevania itself, were also sealed in the underworld throughout most of the series, both of them reappearing on Earth only once every hundred years. But Dracula found so many ways to circumvent that rule that it became more of a "sealed evil in a sieve".
In the Expansion Pack of Baldur's Gate 2, the Bonus Boss is the avatar of a very powerful demon lord. You are asked to reseal him in his prison as he's about to break free. Alternatively, you can fight him in an epic battle. However, if you win, you realize that demon lords in Dungeons & Dragons come Back from the Dead very, very quickly by definition. So it will happen, though not for the rest of the game. Good going.
Well they don't actually die, destroying their physical form returns them to their home plane, in his case it frees his avatar back into the abyss to be reabsorbed by the real one.
Kangaxx the demi-lich is another example. He dies very permanently after underestimating you, however.
Sonic The Hedgehog 2006 has the sun god Solaris, forcibly split into two seperate forms due to an experiment acted upon it: Iblis and Mephiles. Princess Elise served as Iblis' can, with her control over her sorrow being the lid — if she cries, the can is opened and Iblis is unleashed upon the world once more. Somewhere else, Mephiles is sealed away in the Scepterof Darkness until an encounter with Eggman shatters it.
Shadow the Hedgehog made his first appearance as this, though being canned and going evil didn't happen at the same time: his creator screwed with his memories after he was placed in stasis, leading to his whole 'humanity needs to die' outlook.
Sonic Unleashed has Dark Gaia, who was sealed within the planet by his light counterpart a.k.a. Chip in a neverending cycle of planetary death and rebirth.
In Paper Mario The Thousand Year Door, the plan of the antagonists is to summon the Shadow Queen, who can only be summoned into a princess (read Peach). Upon release, the Queen promptly reduces the head of the antagonists to, well, a head, and plans to conquer. Unluckily for her, Mario arrived at the same time.
On the other hand, she recognizes Mario's strength and offers him to work for her. The player is given a Yes or No choice, while the former leads to an instant Non-Standard Game Over.
In Super Paper Mario, Bonechill, a fallen Nimbi, was held in the area of the Underwhere in which the dead villains suffer for eternity among the game overed. He escapes due to an earthquake (often speculated to be the work of the Big Bad, Count Bleck, who is known to be a dimension traveler) and wreaks havoc in the Overthere. Mario, Peach, Bowser, and Luigi fight him and easily destroy him.
In Luigis Mansion, major ghosts that Luigi encountered were once imprisoned inside portraits, but were released by King Boo once E. Gadd captured Boolossus. Eventually they are recaptured by Luigi and put back in their portraits, including King Boo himself... although in the next game he has apparently been released to fight Mario. He is killed this time and next time he is fought (in this case by Peach).
The Shadow Demons in Medi Evil were sealed in the heart of the Enchanted Forest under an iron dome, locked with the Shadow Artifact. In order to get through the forest and to his next destination, Sir Dan Fortesque is forced to free them; he later makes up for it by trapping them in an abandoned castle and dropping it into lava, destroying them.
In the Halo series, the bad guys accidentally release the Flood, a race of alien parasites that were sealed in special facilities all over the galaxy at the end of a cataclysmic war between them and the Forerunners 100,000 years ago. This war ended with the extinction of all sentient life in the galaxy, so it's a wonder why the Forerunners left little pockets of Flood spores for nosey aliens to stumble across. The AI monitor of one of these facilities comments on this (while you're in the middle of fending off a large wave of rotting space-zombies), saying that specimens were kept over after the last outbreak "for study," and remarks that "this decision may have been in error." No shit...
Done again in ''Halo 4 with The Didact, who is most likely the last living Forerunner, being released by the Master Chief.
The Reapers in Mass Effect actually seal themselves after their habitual galactic genocides in order to conserve energy. The only hand the Protheans had in dealing with them was tampering with the Citadel's mass relay after they'd already receded so that they couldn't get back out so easily.
The DLC "The Arrival" reveals that the Reapers left themselves another way in. A special mass relay at the edge of the galaxy that can access any other relay anywhere.
The Grotesqueries in Drakengard, with a twist. Also, no one knows the Sealed Evil in a Can exists except possibly the Big Bad. They're concerned about some other thing that comes out when those seals are broken.
In Guild Wars, Palawa Joko suffers this fate. Then there's Abaddon and everyone else locked in the Realm of Torment, including the Titans from the first game. Ultimately, in an attempt to stop Varesh Ossa from opening a gate to the Realm of Torment, you have to let Palawa Joko out of his prison.
In Shadow of the Colossus, except there are sixteen cans wandering throughout the area. Most notable with the final Colossus though. Besides having a name that literially means 'evil' in Latin, the only possible way you can reach it is to have killed all fifteen other Colossi ingame. Might also apply to Dormin as well, if you're part of the group that thinks he really is evil.
Quest for Glory is fond of this one. In fact, every game following So You Want to Be a Hero centers around such a plot.
Toward the end of Trial by Fire, it is revealed that Ad Avis is trying to summon Iblis, a powerful and evil djinn.
In Wages of War, the Demon Sorcerer attempts to free the Demon Lord. (If he succeeds, the Demon Lord's first act is to cast Thermonuclear Blast on the immediate area. As it turns out, this is a legitimate spell, and can be learned in the fifth game.)
In a minor twist, in Shadows of Darkness, Avoozl, the Dark One, wasn't quite sealed properly, and the surrounding countryside has suffered for it. Even as the two antagonists (one new, one old) try to release it, it is only through their actions that it can be put away for good.
Dragon Fire has a twist of its own - there is a villain working behind the scenes and trying to unleash the Dragon of Doom, but by this point in the series, the hero (under extenuating circumstances) has become strong enough at this point to just kill the thing.
A Mess O' Trouble (an excellent Mac WorldBuilder shareware Adventure Game) has two godlike creatures trapped inside time dilation bubbles in some ruins. You know from local historians (and abominations lying around in the ruins) that their civilization was practically constructed by a good creature and then fooled into nearly destroying itself by a bad creature. One is a beautiful Energy Being, the other a dull-looking lizard man. Guess which is which?
Final Fantasy III gives us the Cloud of Darkness, the living essence of the power of the Dark (as opposed to the Light of the heroes' world.) The game implies that Xande's machinations allowed it to take form, but it would have remained sealed away in the Dark World had it not been for him opening a portal leading straight into it. The Dark Warriors imply that they fought the Cloud 1,000 years ago, when it was Light surrounding Darkness, and got it Canned within the Dark World. Xande was nothing but a can-opener.
Zemus in Final Fantasy IV, who, despite being sealed in the Lunarian Moon was still able to influence events in the world in an almost successful attempt to effectively kill all humans. Notably, he is never released from his can; you raid it.
Final Fantasy V's previous generation of heroes, the Braves of Dawn, used the power of the Crystals to seal away Exdeath, who then surreptitiously began to drain the power of the Crystals (either personally or through manipulation.) Additionally, the player learns that, prior to Exdeath, the sorcerer Enuo was the first to harness the power of the Void, and waged war with it until he and all his obscenely powerful demons were thrown into the Dimensional Rift. The Advance version expands upon this by letting the player explore Enuo's prison and vanquish him for good.
Also in Final Fantasy V there once was a tree in the Great Forest of Moore used to seal up evil spirits. Eventually, the power of those spirits gave the tree sapience, power, and a whole lot of evil. That tree became Exdeath; a prime example of sealing so much evil away that the can itself turns evil.
The Warring Triad of Final Fantasy VI, who started the War of the Magi, sealed themselves away after realizing the destruction they had wrought upon the world, and the Espers hid them away in their own underground kingdom. Then Kefka came and released them, destroying the balance of magic and devastating the world. It also released Humbaba, Deathgaze, and the eight dragons who are released during the apocalypse.
Jenova of Final Fantasy VII is a basic example of the trope. In the sequel movie Advent Children, what's left of her is stored in a literal can.
In Final Fantasy VIII, Laguna Loire tricks evil sorceress Adel into walking into a specially-prepared technological "tomb" in which he is able to seal her considerable powers. Then he launches it into space and spends the next seventeen years making regular trips to monitor the seal. Predictably enough, catastrophe eventually lets her loose again, but by that point Laguna's son is well-equipped to kill her off for good.
Shuyin of Final Fantasy X-2 is a special case. In one sense, he is still sealed within the Den of Woe, but in another sense he is free to wander around within the body of first Nooj, then Baralai. Also, while his goal is indeed to break free of his prison and destroy the world, this is because he's a Woobie, Destroyer of Worlds, not an Ultimate Evil.
The Tonberry enemies in the Final Fantasy series also appear to be like this. Despite their goofy appearance, their Grudge attacks suggest that they're like vessels for all the malice and wrath of slain monsters.
In Persona 3: FES, we find out that said main character has become the seal. And it's in place not to seal Nyx from attacking Earth. It's for sealing Earth from summoning Nyx itself.
The Snow Queen Mask in Persona is definitely one. It's kept in a gym storage room, in a box sealed with MAGIC TALISMANS, and after going on That One Sidequest in which everyone warns you about the horrible past of said mask, you can just decide to open the box like nobody's business and walk off with it completely unpunished.
Kirby Squeak Squad plays with this one a little. What started as a hunt for stolen strawberry shortcake leads to Dedede getting smacked down on false suspicions, Kirby chasing all over the world to get his snack back from the titular menace only for the chest allegedly supposed to hold the shortcake stolen away by Meta Knight, and when HE gets smacked down, the Squeaks grab the chest and let loose Dark Nebula. For such a simple protagonist the plot for these can get quite complex, especially given Meta Knight grabbed the chest away just to prevent Dark Nebula from being released. The best part is that through all of this, you get the feeling that Kirby is still being motivated only to retrieve the cake.
Turok 2: the objective is to stop the Cosmic Horror Primagen from being unsealed from his can.
Dhaos, the villain of Tales of Phantasia, was sealed away by the protagonist's parents, but was released early on in the game by a minor villain he had been manipulating.
Boktai 2: Solar Boy Django has a textbook example in its Big Bad, Jormungandr.
The Japan only sequel has a similar deal, except its cosmic horror, Vanargand, was sealed on the frickin' MOON.
The world of The Magic Candle was narrowly saved from the immortal demon lord Dreax when a few heroes managed to trap him in a candle flame. Keeping him there is the daily task of 44 mages... who have just disappeared. The seal is now critically weakened, leaving the player a set number of days to find out how to fix it.
Somewhat unique in that the point of the game is to reactivate the seal, not simply to grind yourself to the point where you can just kill the damn thing (because doing so is impossible, at least by the terms of the game world).
Fire Emblem: Path of Radiance alone uses the trope straight, with the characters believing that Lehran's Medallion contained an evil god that flooded the entire world save Tellius. So at the end they not only the heroes fight Ashnard in order to liberate Crimea, but also to prevent him from unleashing a dark god. However the true nature of the relic is revealed in the sequel Radiant Dawn, and the heroes are the ones who free Yune, the Goddess of Chaos, rather then letting the negative energies of war do it. As it turns out, Yune was actually Sealed Good in a Can who just happened to mess up (the Great Flood); in fact, the Big Bad is Ashera, the goddess everyone had been praying to throughout both games, who purged her emotions (forming Yune) to avoid another Great Flood.
Dwarf Fortress has what is popularly referred to in the community as "Hidden Fun Stuff". If your dwarves tunnel far down enough, they may breach a secret chamber containing demons which are powerful enough to bring the fortress to its knees. It's possible to kill them, though.
As of the latest update there are now "Demonic Fortresses" which are a bit like the pits, but the pits have been replaced with hell itself, which you simply reach by digging far enough, implying most of the physical structure of the planet is a caverns made of an unmineable, indestructible, impossibly heavy Unobtainium who's exits are blocked by another Unobtanium which is very valuable, light, and hard. And every Demonic Fortress contains a hole straight to Hell, blocked by a masterwork sword made of the latter type of Unobtainium. As for Hell itself, it contains so many demons that the game doesn't bother counting them.
In Age Of Mythology the cyclops Gargarensis is on a mission to free Kronos from Tartarus in return for godhood. He fails. Kronos gets out in the expansion, but gets killed by Gaia.
In Metroid Prime: Hunters, "the ultimate power" broadcast in a telepathic message throughout the galaxy is actually the sealed evil Gorea, originally a Giant Space Flea run amok and the presumed source of the message. This is one of the few cases where the good (the Alimbics) weren't strong enough to kill the evil, just entangle its energy with theirs in the Seal Sphere and hide it in a pocket dimension. You arrive at the Seal Sphere only to see the other Hunters pounding away at it like idiots. They break it open, then stare as the core of the Seal Sphere (the Alimbics' energies) is snatched by Gorea, who proceeds to impale all of them with tentacles from the Sphere and steal their energies (weapons). You saw this coming, or at least you WOULD if you've scanned at least 25% of the Alimbic lore hanging around the place... Anyway, this leaves you to clean up the mess (kick Gorea's ass).
The titular creature from the first Metroid Prime game was sealed within he impact crater. In the original version, the Space Pirates managed to free it by digging under the seal, although it later escaped from them and returned to the crater, and you have to open the seal to fight it. In the European release/Player's Choise version, it was never released.
The Legend Of Kyrandia III: Malcolm's Revenge has the player play as a Sealed Evil in a Can, who is rather dismayed to discover that being unsealed does not include getting his awesome magical powers of doom back, leaving him running around with no powers in a fantasy kingdom where everyone hates his guts.
Averted and parodied in Septerra Core. The game's intro movie and backstory tell about a great battle in which Marduk (the world's Crystal Dragon Jesus) defeated Gemma (the local Satan equivalent). In most RPGs, at some point towards the end Gemma would be resurrected and become the final boss. The main character even speculates that this is going to happen after hearing the tale about the battle between Marduk and Gemma. In response, The Obi-Wan remarks that such a plot twist would be rather silly, and only happens in stories. Sure enough, Gemma never comes back, and the final boss of the game is the character who's been the main villain from start to finish, the Knight TemplarEvil Overlord Lord Doskias.
Phantom Brave features an example as the main antagonist, the demon Sulfur. Rather than the usual thousands of years of imprisonment though Sulfur is capable of coming back every 30 years, and during his imprisonment can extend enough influence into the world to wreak havoc.
Parodied in Makai Kingdom as Zetta seals himself in a book after he destroys his own netherworld. Hilarity Ensues as he tries to get his body back.
All games in the Ys series use this trope, e.g. Darm in I and II (who was disguised as the Black Pearl, also an Artifact of Doom), Galbalan in III, the Ancient City and Arrem in IV, the lost city of Kefin and its king, Jabir, in V, and the Ark of Napishtim in VI.
In the Infocom text game Enchanter, your job is to defeat the evil enchanter Krill without disturbing the Cosmic Horror that's sealed below his castle. The tie-in novel by Robin Bailey takes the tack that your character accidentally did release the thing, and now it's up to the book's protagonist to stop it.
The City of Villains is practically filled with these: Bat'Zul under Cap Au Diable, the Leviathan under Sharkhead Isle, Shiva in Bloody Bay... and the City of Heroes isn't lacking in them either, as Dark Astoria apparently houses the sleeping dread god of the Banished Pantheon, and the Kaiju that may still be in battle with Talos underneath Talos Island... Also, both sides can get involved in the escape of the Reichsman, Nazi with the power of the gods.
Marathon Infinity starts out with a grim message from Durandal about the W'rkcacnter getting loose from Lh'owon's sun, due to the Pfhor using the trih xeem on it. The W'rkcacnter cannot be fought directly, and is only defeated by the player jumping between different places and timelines, before the player reaches a Jjaro space station that is able to turn the sun into a black hole, thus trapping W'rk before it (them?) escapes.
In Pathways Into Darkness, the Marathon games predecessor, a modern-day Special Forces team must prevent a W'rkcacnter from escaping from its can.
Speaking of Bungie, the main plot of Myth: The Fallen Lords is this, and it's reanimating corpses and whatnot. After you all but lose the war, you manage to kill it.
A more literal example is The Watcher, a powerful Lich who was imprisoned in a cave by a charm on his hand that would turn him to stone if he tried to leave. Ultimately, he chose to cut that hand off. He finally met his doom when an arrow was fashioned from the bone of the hand that was left behind and turned him to stone after striking him.
In Dead Space, the Marker seals the infection that turns corpses into horrific alien monsters (it was actually a manmade knockoff of the real marker). Anyways, the Marker-Worshipping ScientologistsUnitologists discover the Marker in the midst of mining Aegis VII and move it off its pedestal. Bad things occur.
The hook and most the line of Arcanum's plot involved the player character being a Chosen One prophecied to defeat a Big Bad, last known to be sealed in a can. Later it's revealed that many evils are sealed in that can, and by the time you finally wormhole your way inside, the Big Bad has done a Heel Face Turn long ago, after having been overshadowed by an Evil Overlord you must defeat instead.
The "can" in question is in itself a Sealed Evil, although, becoming a hero, this was obviously subverted.
Wario Land games have had a few cases of this, with Wario Land 3 having Wario spend half the game trying to 'help' a mysterious figure trapped in the music box, who turns out to be Rudy the Clown, which then tries to take over the world. Wario World had him accidentally unleash the sealed evil in a can at the very beginning, aka the Black Jewel, which was taken from some kind of treasure chest by Wario and his obsession with treasure, and that then turned his entire castle into a parallel dimension of sorts and what not.
Jedi Academy: The sealed evil takes the form of an ancient Sith Lord, whom the game's big bad is naturally trying to resurrect, thinking she will be rewarded. The Sith Lord has other ideas.
EarthBound: Giygas is first encountered in the Devil's Machine, which seals away his warped consciousness. Subverted in that Giygas can still damage Ness and his friends while sealed away, but played straight when Pokey unleashes Giygas' true form by turning the machine off.
Mother 3: When his mech runs out of power, Pokey/Porky retreats into his Absolutely Safe Capsule — which can't be opened from the inside or outside. Not quite SEIAC, as this capsule cannot possibly be opened, damaged or otherwise altered by any earthly or divine means.
In what is possibly the worst-sealed can ever, Pac-Man. He kills the ghost, sealing it in the little box in the center of the screen. Three minutes later, it escapes again, and poor Pac must kill it over again. Perhaps he'd have better luck if he gave his little ghostbox a lid.
Well before the start of the Geneforge series, the Shapers discovered a startling new technology that could imbue ordinary humans with incredible magical powers. When they discovered some of the side effects involved (such as Suicidal Overconfidence, a violent temper, and in extreme cases, outright Body Horror), rather than take any steps to destroy this technology, they simply abandoned the remote island outpost where it was discovered, and declared it off limits under penalty of death. Fast forward a few hundred years: A band of explorers from across the seas happens upon the abandoned outpost and all its forbidden goods. Things go downhill from there.
In fact, the Shapers do this constantly. Their laboratories, workshops, and schools are designed to be sealed up quickly should anything Go Horribly Wrong.
Not just should. It's said at one point that more often than not something does go wrong.
In Romancing Sa Ga: Minstrel Song, the god Saruin was sealed away via the Fatestones; naturally, his minions are trying to 'correct' this. However, an even better example is the Jewel Beast: a monster poised to destroy a whole country if awakened. Even if the player manages to delay its awakening — no easy feat by itself, given the precise timing and difficult sequence of events that involves — they can't stop it unless they enter its lair while it's still sleeping. It's one of the harder fights in the game.
Orochi in Ōkami is a definite example of this trope.
In Phantasy Star I, II, and III, you find the big bad end boss Dark Force/Dark Falz/Dark Phallus (depending on translation) in a literal Pandora's Box in the final dungeon.
In IV, you discover that the Profound Darkness is one of these, and it has been creating Dark Force/Falz/Phallus for thousands of years (please note that there's a thousand year gap between I and II, and between II and IV'').
Earth 2160 has the traditional sealed-ancient-evil-alien-race-beneath-the-surface-of-Mars for the first half of the game. Then some Dutch nerd learns to control them, and it all ends badly(-er).
A subversion, Lavos was an alien that burrowed into the earth and then unleashes the apocalypse many ages later as part of its natural life cycle. Essentially, it seals itself in the final can and breaks out when it wants. The villains of the game attempt to awaken him to harvest his power, with the apocalypse being a byproduct of this.
In the LucasArts computer game LOOM, Bishop Mandible unleashes Chaos by ripping open the fabric of the universe near a graveyard.
In Prototype, Elizabeth Greene, the host of the Redlight Virus is sealed in the Genetek building. Badly. The protagonist might also count as a Sealed Evil In A Can, although in this case it's more like Sealed Evil in a Vial.
Vampire: The Masquerade - Bloodlines features a memorable subversion — the MacGuffin of the game is a sarcophagus that supposedly contains an Antediluvian (very old, very powerful vampire). Everyone is trying to make a move for the sarcophagus, partially because the presence of such a thing might be a herald of Gehenna — but also because a low-generation vampire represents a massive power grab for anyone willing to commit diablerie (the consumption of another vampire's soul). Well, the Prince has been pushing you around all game in an attempt to claim the sarcophagus, and when it's finally opened... the only thing he finds is a lot of C4. And a note from the guy who set the whole thing in motion. Boom.
The Dark Star from Mario & Luigi: Bowser's Inside Story. It was imprisoned in Toad Tunnels (possibly due to the threat it posed when Smithy used it, lol, he uses an attack called Dark Star in Super Mario RPG that is the most devastating attack) until it is released by Fawful. Its core is destroyed by the Mario Bros. and its main form is killed by Bowser.
In Mario & Luigi: Partners in Time, at the end it is revealed that Princess Peach seals Elder Princess Shroob, the leader of the Shroobs, inside the Cobalt Star. When the star is pieced back together, she is released, and fights the Mario Bros. She is defeated, and eventually killed when she possesses Bowser and the Mario Bros. trick him into hitting her with his fireballs while aiming for them.
Similarly, possibly the entirety of the Golden Pyramid in Wario Land 4, and the Black Jewel in Wario World.
The demons in Doom 3. Sealed in a can until Dr. Betruger teleports himself and the Soul Cube into Hell. They were sealed back into the same can at the end, as well...
Heinrich I, in Return to Castle Wolfenstein. Doubly so, given what he does to Blavatsky. Earlier in the game, there's Olaric, who is accidentally unleashed by Helga von Bulow when she tries to take the Dagger of Warding.
In Borderlands, the Vault only contains—as far as the player is concerned—a monster called The Destroyer who is "immortal in his own realm". Sadly, this final fight is easier than a single monster from the previous zone. The Vault also opens every 200 years, which raises the question of it really is a sealed can.
Malefor, aka The Dark Master from The Legend of Spyro series. He was born as a purple dragon, like Spyro, some countless generations ago. He was taught how to master the elements, but kept gaining more power, resulting in the Elders banishing him to exile. He took on the title of The Dark Master, where his malice was so great that it split the Earth, creating the Mountain of Malefor, also known as the Well of Souls, where he was imprisoned. In A New Beginning, he sends out Cynder to open the convexity portal to free his soul, which she succeeds in, though Spyro frees Cynder from his control, causing the portal to implode. In The Eternal Night, Gaul uses the lunar eclipse of the celestial moons (that causes non-stop darkness for a short while) to seemingly resurrect Malefor. But it's revealed by Malefor in Dawn of the Dragon that this was merely all a ruse to get the real one to free him to the Well of Souls to do so, who was it? Poor Spyro.
Also, the Destroyer counts, as its sole purpose for existing is to destroy the world but it slept below a volcano until Malefor awakened it to destroy the world. A rare case of one Sealed Evil In A Can freeing another.
In the Touhou game Perfect Cherry Blossom the evil cherry tree, the Saigyou Ayakashi, is sealed up by the dead body of Yuyuko Saigyouji. At the same time, the tree seals her, preventing her from reincarnating, so she wanders as a ghost. In a wierd twist, Yuyuko eventually forgets her life as a human, up to and including why she died or who is sealed beneath the Saigyou Ayakashi. This leads to her trying to ''undo' the seal that she placed in the first place, because she forgot she did it.
The player characters in Undefined Fantastic Object think that the incident is releasing one of these, however Byakuren is very much a Sealed Good in a Can.
From the perspective of the Buddhists, the Taoists in Ten Desires are this, what with that whole religious war thing. As usual for Touhouthey aren't evil, but neither are they particularly good.
seems to be the case with the Kingdom of Sorrow in Klonoa 2: Lunatea's Veil. As it turns out, it was sealed away because no one wanted to remember sorrow, and the King of Sorrow tried to undo the seal so everyone could remember sorrow.
The Devil May Cry series. Every. Single. Installment. ...except the fourth. That one just needed to be awakened rather than unsealed and at the end of the first one Mundus is resealed in the can..
The draconic Old Gods of the Tevinter Imperium in Dragon Age: Origins were, according to the Chantry, banished to the depths of the earth by The Maker to slumber for all eternity. The Darkspawn are somehow able to hear the Old Gods' Call and devote centuries of effort tunneling through the earth in search of them. When they finally discover an Old God, the Darkspawn taint immediately corrupts the ancient dragon, turning it into an insane and twisted shell of its former self — an Archdemon. The new Archdemon then commands the Darkspawn hordes in a bid to kill everything — a Blight. By the time the game starts, the world has already suffered through four such Blights. One of the biggest secrets that the higher-ups of the Grey Wardens keep from the rest of the Order is that they know where the Old Gods are buried.
In a DLC of Dragon Age II, Hawke finds an old Grey Warden fortress, which turns out to be a prison for one of the original Darkspawn - a Tevinter mage who attempted to reach the Golden City and was cursed by the Maker. The magic seals have held for thousands of years, but are finally starting to give out.
In Resident Evil 4, the parasitic Las Plagas were sealed away for eight generations before the start of the game.
Arcanum Of Steamworks And Magick Obscura has the void, an alternate dimension where the Elven Council banished 5 Evil beings: A demon with insatiable hunger, the murderer who killed Arcanum's last dragon, a genocidal barbarian king, and two corrupt wizards. The player character has to undergo banishment so they can destroy the Big Bad, Arronax Kerghan, before he can regain his freedom.
Akron, the Final Boss of Epic Battle Fantasy3. He notes in his Boss Banter that he has been defeated and sealed away countless times through time immemorial — but in the end, his enemies all succumbed to time while he always returns.
Shivers has the Ixupi, ancient soul-sucking Mayincatec demons who were sealed into pots with talismans. Millenia later, an itinerant archaeologist digs them up and puts them in a museum. Then two kids sneak in the museum and break them open.
Return To Krondor presents the Dark God as this. The Dark God does not get released, but the ending makes it clear that the person trying to unseal it has not given up.
Might And Magic VII has a rather simplistic sealing liable to be done by the player characters: the medusa crawling around in the sub-level of an abandoned mine have developed an immunity to magic. As a class promotion quest, you get sent to sabotage the elevator to keep them down there.
A significant portion of the plot of Brave Fencer Musashi revolves around this. The first major quest in the game involves Musashi being sent to collect Lumina, the legendary greatsword used to defeat the Wizard of Darkness; a significant portion of the rest of the game revolves around Musashi questing to recover the elemental Scrolls in order to power Lumina up enough to take out the Thirstquencher Empire. Unfortunately, it turns out the voice which set Musashi on this quest in the first place, a voice originating from Lumina itself, was actually the Wizard of Darkness himself, not destroyed but sealed within the sword. Guess what the only things holding him back are? If you guessed "the five Scrolls and the Crest Guardians they're connected to," you win the kewpie doll.
Lightning Legend Daigo No Daibouken has Dragless, a legendary and all-powerful Demon King who rampaged through the Kingdom of Japone 450 years before the story's proper, destroying everything on his way. He ultimately was defeated and sealed away in the deepest ends of Mt. Ohsore by the young hero Taikei Raioh, but by the start of the game he has finally freed himself, and it's now up to the descendant of Taikei, Daigo, to defeat him for good.
Played with in Dragon Age: Origins. The Darkspawn seek out the seven ancient dragon gods buried within the earth, and when they find and awaken one it becomes the Archdemon and leads them in a massive invasion of the surface world - but the sealed gods were not necessarily evil until tainted by the darkspawn, making them more like Sealed Badass in a CanGone Horribly Wrong.
In Dragon Age II Hawke can fight several powerful demons that were sealed away in and around Kirkwall. The "Legacy" DLC revolves around the Hawke family's connection to an ancient Sealed Evil In A Can Corypheus one of the original Tevinter Magisters who brought the Darkspawn Taint to Thedas whose subconscious efforts to free itself have brought danger to Hawke's doorstep. There's also ANOTHER uber-monster sealed right outside the prison housing him, but that one's an optional Bonus Boss.
The Antarans from Master Of Orion 2: Battle at Antares. They are an ancient and powerful race who were banished to another dimension by the Orion Empire. However, they learned how to break out of their prison and were able to warp raiding parties to attack colonized worlds while preventing others from invading their prison-turned-stronghold. Nice job breaking it, Orion.
The Dread Lords from Galactic Civilizations 2. The Dread Lords had a pocket dimension which they had used as a base for their fleets. Their enemies, The Arnor, used this against them by sealing the last of their empire in the dimension. Later on, the Dregin found the lock to the Dread Lord prison. Thinking that is was an ancient weapon, they activate the device, allowing the Dread Lords to escape and wreak havoc across the galaxy. Upon seeing this, the Drengin realize their mistake and decide to leave the others for dead.
In Valis II, Cruel King Megas had been sealed away long ago, but was released when rebels battling the forces of the fallen Lord Rogles broke the seal and opened the Forbidden Door. The result was to turn Vecanty into Hell on Earth.
The entire Arc The Lad series revolves around this trope with the Dark One. He starts every game being sealed, winds up being unsealed at some point, and then gets re-sealed by the end of the game.
In Shining Force II, evil Zeon is accidentally released by the good thief Slade who steals the crystals sealing him.
Shining Force III's overall plot is about a secret cult reactivating ancient weapons to create enough chaos to allow the Vandals to return.
Shining The Holy Ark is all about how a group of low powered Vandals want to release one of the most powerful Vandals ever; so he can recreate the 1000 Year Kingdom.
Shining Soul sees you seal away Dark Dragon for at least a 1000 years.
In Resident Evil Code Veronica, an experiment with the Veronica virus on Alexander Ashford mutated him into a grotesque monster codenamed Nosferatu, who is imprisoned in Umbrella's Antarctic base until our heroes arrive. Alexia also counts somewhat.
The Tyrant in ''Resident Evil', which is released by Wesker near the end of the game. In the bad ending, it escapes from the facility.
In the Mortal Kombat series, the fallen elder god Shinnok is sealed in the Netherworld. The Realms themselves are actually the Can keeping the One Being sealed. Merging them would allow the One Being to return, which is why the elder gods resist any attempt at unification.
The entire point of most the rituals in the Fatal Frame series is to make sure the sealed evil (specifically Hell itself) stays that way, though naturally they always eventually fail and plunge the area into endless suffering,we'd have no game series otherwise
In the final route of Duel Savior Destiny instead of killing Lobelia after she is beaten, her soul is trapped via alchemy when she tries body hopping.
The Order of the Stick features The Snarl, a monster formed from tangles in the fabric of reality, and sealed within the world itself.
Also subverted with The Creature in the Darkness, who Xykon and Redcloak think should be evil and scary (and accordingly, they keep it locked in a box), but for the most part is just hungry and clueless, verging at times on Too Dumb to Live.
Subverted in 8-Bit Theater. Red Mage places the fire demon Kary in a Bag of Holding and freezes it with a powerful Ice spell, with the idea that she will remain sealed until they are powerful enough to defeat her. White Mage simply smashes the frozen bag in revenge for the death of Black Belt.
In Girl Genius, the Other is a being of such extreme evil that it wants to enslave the world... and doesn't really care who dies in the process. It was eventually defeated, but nobody knows HOW... except maybe the parents and uncle of the protagonist. It left a machine behind with a copy of itself, which it then imprinted on the protagonist (unsealing it), who is the daughter of the Other, or rather, taking into account certain implications and statements that lend themselves towards it having been an actually ancient evil, it simply possessed the protagonists mother, and hundreds of other people through time, before finally taking possession of the protagonist, temporarily.
Inverted in The Way of the Metagamer: the evil is sealed within the Book, and does not escape... but the heroes are forced to follow it into the Book.
The Axe of Prissan in Goblins acts as a prison for an immensely powerful demon lord, whose very existence threatened the mortal plane. The enchantments binding the prison will gradually break down if the axe is not used for good, or even faster if used for evil. As such, it has enchantments layered on it to ensure it will aid any paladin who encounters it and refresh the prison.
Many, many things contained by the SCP Foundation. One, SCP-076-2, had the particularity of coming with his own (leaky) can, SCP-076-1, and the SCP (after many Pyrrhic Victories keeping it in the can) eventually decided to try and work with him; predictably, it didn't end well.
Neopets now has its very own Sealed Evil In A Can, as of the end of the Return of Dr. Sloth plot event that happened January 29 - March 15, 2008. The comic is here, and spoilers are here: Dr. Frank Sloth is the sealed evil. The can is the Space Faerie's token. Roll your mouse over the very last panel of the last chapter, and you'll see the token, which was not destroyed in the explosion of the ship, floating through space. When it gets most of the way across the panel, a pair of red eyes glow from within...
Phantasia has more than one of these, of varying degrees of world-destroying power.
Trigon in season four of Teen Titans, where his daughter Raven becomes his portal into the world, allowing him to turn every creature in the biosphere into stone and cover the planet in lava.
Also, the dragon Malchior in an earlier episode qualifies, sealed in one of Raven's spellbooks.
Most seasons of Jackie Chan Adventures involved the cast attempting to reseal escaped Sealed Evil In A Can once using a jar-like object. In the series, this is justified by the fact that destroying evil will only allow a different (and probably stronger) evil to take its place. Better then to keep around the evil threat you already know how to deal with, than risk leaving the way open for something far worse to come up that you may not know how to deal with in time.
In other words, the devil you know is better than the one you don't.
The singing, dancing frog who ruined a man's life in the Looney Tunes short "One Froggy Evening" was placed into a cement slab and freed several hundred years in the future. The frog was also found by the man in question in that cement slab, so he may have been taken out of and put back into the slab many, many times by all the men whose lives he had ruined.
This is based on the story of a real (not evil) horned lizard that was sealed in the cornerstone of a courthouse (long before they were on any endangered species list). 31 years later the stone was opened and the horned lizard was alive and lived on for almost a year afterward.
Vilgax, from Ben 10, tends to be put in a can of whatever sort between appearances, be it a healing chamber, a block of ice, or a pocket dimension. He's slightly unusual in that we see him out of the can first.
And in the same show, Ghostfreak is an odd example of evil that got sealed in a can accidentally, his DNA sampled for the show's Clingy MacGuffin so that the wearer can turn into him, and the personalities of his species being encoded in their genes somehow. Eventually, he gets loose and becomes Ben's Enemy Without.
Hades, Greek God of the Underworld, in Justice League. Released by Felix Faust in the hopes that Hades will grant him "ultimate knowledge" in return. Hades naturally betrays Faust by causing him to instantly age to an old man since "Ultimately, pain and suffering are all humans will ever know."
In the prequel episode of Code Lyoko, we discover that the dormant Supercomputer was sealing XANA for 10 years. It is Jérémie, by turning it back on, who unleashed the malevolent program (plus his future girlfriend) on the world.
The Care Bears Movie had the Evil Spirit, whose can was a locked book of magic spells a young boy, Nicholas, opened. The spirit is powerful but, since it's confined to the book, needs Nicholas to cast its spells; he becomes progressively more evil in the process. The Power of Friendship helps him come to his senses and he helps close and relock the book, ending the threat.
In Animaniacs, the Warner Brothers (and their sister Dot) were Sealed Zany in a Water Tower. In this case, it was more Sealed Chaos in a Can.
Kim Possible had some sort of a sealed evil monkey man who petrified people in one episode. His name fit him perfectly, The Yono
For 4 million years, the Ark held the Decepticons and Autobots in stasis, under a volcano... until volcanic activity shook things up and woke up the evil Decepticons.
In Cosmic Rust, there's a dead planet with radio beacons warning travelers to stay away or die horribly. The Decepticons plunder it, and in the process, catch the metal-eating plague called Cosmic Rust.
In Return of Optimus Prime, the Hate Plague spores were sealed inside a star after their last outbreak. Unfortunately, the star went nova.
Starscream himself could be considered Sealed Evil in a Can in the episode Starscream's Ghost; his ghost first appears after Octane tumbles into the Decepticon crypt and knocks over the ruins of Starscream's grave marker.
Beast Wars brought us Protoform X a.k.a. Rampage. He was the result of Maximal experiments to produce an immortal super-soldier by copying Starscream's mutant spark. They got that part right in the form of an unkillable serial killer that slaughtered human and cybertronian alike. After eventually capturing him, the Maximal Elders sealed in up in a stasis pod then turned him over to Optimus Primal's to dump on some desolate asteroid since they could figure out how to destroy him. Several adventures later and the monster was unleashed again and recruited by the Predacons.
Deconstructed in Transformers Prime. After Unicron's defeat by Primus, his body was cast away into the depths of space. His gravitational pull attracted matter over billions of years which coallessed into the Earth itself. Unicron's physical form is the Earth's core, but he can control the mineral deposits on the surface and create golems of himself, among other things.
In Di Gata Defenders the plot of the first season is for the titular Defenders to reseal an obscenely powerful entity known as the Megalith that the seasons' Big Bad used to take over most of the world a generation ago. However, the defenders decide on a change of tactics after finding out that not only has this thing been sealed and escaped numerous times in the past, but that it gets better at unsealing itself each time.
The Megalith happens to be keeping another evil sealed in another dimension.
SWAT Kats: In the first episode, the Pastmaster is Sealed Evil in a Treasure Chest. We don't learn he exists until after he gets unsealed.
There's also the Mad Kat The Insane Jester, who was sealed in a jack in the box.
Felidae's Claudandus means "something that must be sealed".
The Real Ghostbusters played with this trope on occasion, notably in the episode "Knock, Knock". They even played with Chthulu in one episode.
In an episode of Sonic Sat AM, Robotnik steals a computer of magic spells from the formerly evil wizard Lazar, and Sonic attempts to get it back. When asked why he can't just destroy the computer, Lazar says that would release all the evil it contains.
Valtor from Winx Club may count as sealed evil in a block of ice, until the Trix released him in the beginning of season three.
The position of Phobos and several of his most powerful minions for most of the second season of W.I.T.C.H. until he gets released by the heroines. Nerissa was also once a Sealed Evil In A Can, but she escaped several decades before the series begins.
Buzz Lightyear Of Star Command had Natron the First in the aptly named episode "Ancient Evil". After he is defeated and returned to his tomb, Mira melts the door to it. Hopefully this will keep him sealed.
Chiros, the secondary antagonist of Kong The Animated Series. Imprisoned in a stone tablet that is implied, by Harpy cautioning the gargoyles moving it, would turn out bad for Chiros if it was broken (whether it will actually kill him or simply prevent him from being released ever again is unknown). It is also unknown why it was never destroyed the first time he was sealed inside it. At the end, Chiros is released, but Lua opens up a portal and Kong spins him by the tail and throws him back in, sealing him inside the tablet again. Kong immediately smashes the tablet.
The villain of the first two episodes of season two, Discord — the evil Spirit Of Disharmony who ruled Equestria as a land of chaos and suffering — was trapped in a stone prison over 1000 years ago by Princesses Celestia and Luna using the Elements Of Harmony. After they lost their link to the Elements Of Harmony, the seal keeping him imprisoned began to break, and finally a little bit of chaos happening right next to it (thanks to the Cutie Mark Crusaders getting in a fight) gave him the strength to escape and begin his reign of chaos and disharmony anew. In the end, the Mane Cast put him back.
Then ultimately subverted, as in a season 3 episode, Celestia has the Mane Six release him in order to redeem him. It works.
"It's About Time" reveals that there're a bunch of these things sealed away in Tartarus that are guarded by Cerberus.
The IDW Comics have this with Queen Chrysalis and the Changelings ending up imprisoned in their own castle after their second defeat.
In The Godzilla Power Hour, the Cyclops was so invulnerable that even the Sufficiently Advanced aliens who discovered it couldn't destroy it, so they trapped it on an island behind an impenetrable force field. The sucker's so tough, even Godzilla doesn't successfully destroy it at the end, so the crew just ends up trapping it back behind its force field.
Simon and Snarf in Trollz; while the Magic of the Five was sufficient to release Snarf, Simon had to trick the girls into helping him, as he could only be freed by someone pure of heart helping him of their own free will.
In Adventure Time, Marceline's father, the Lord Of Evil, is sealed in the Nightosphere. Finn frees him, not knowing how evil he was. In the end, Finn manages to seal hime back into the Nightosphere. Even worse is the Lich, the Ultimate Evil who was imprisoned inside amber within a great tree by the legendary hero Billy. He finally broke free during the season 2 finale.
In Mucha Lucha: The Return of El Malefico, El Malefico was imprisoned in the core of the Earth for 100,000 years. He used The Flea to trick Rikochet into freeing him by reading a passage from the Code of Masked Wrestling backwards. At the end, El Malefico is defeated and he is sealed back up again.
The Red Sentients in Hot Wheels Battle Force 5. They were sealed away in five seperate Battle Zones by Zemerick when he betrayed them. At the end of season 2, Krytus is freed by a traitor named Praxion (whom he promptly drops off a cliff) and proceeds to release the rest of his team from their own prisons. The rest of the Red Sentients were all frozen by Sage before they could join Krytus in his multiversal conquest. These are ultimately a subversion, as it turns out they're just as tired of the war as the Blue Sentients are when they're released and gladly make peace instead. They then reseal Krytus in a block of ice on a distant world as punishment.
In an episode of Alfred J Kwak, Alfred encounters the Evil Spirit of Darkness, an ancient demon who caused so much torment and destruction that God locked him inside a magic bottle.
The mischievous spirit in "The Box Of Dirty Tricks", which is sealed inside a box in an attempt to contain it from doing anyone any harm. Not that it stops the spirit entirely from doing its dirty tricks upon whoever possesses it.
Mystico the goblin from "Nobody Smurf", who was sealed inside a fountain and was accidentally released by Nobody and Clumsy Smurf when they knocked over a goblet near the fountain that they were not supposed to touch.
The druids in a tree in the episode "The Smurfs' Time Capsule". Only their leader managed to escape so that he could get the Moonrock Amulet and free his brothers when the light of the full moon hits the amulet. The Smurfs stopped his attempt and sealed the druid leader back inside the tree.
In Gravity Falls, the wax statues were locked away for ten years before Soos stumbled across them and they were able to seek their revenge.
Yucca Mountain Repository is a giant storage facility for nuclear waste. As much of the waste has half-lives long enough to still be pretty dangerous after 10,000 years, a lot of research has been done into the subject of how to do Sealed Evil In A Can correctly. For instance, the stability of the landscape needs to be taken into consideration; in 10,000 years, this part of Nevada might not be a desert. With a higher water table, the waste could leak. Language is also an issue, as languages are dynamically changing (consider the difference between Old English and modern English), a sign saying "Warning: horrible death lies within" might simply be inviting disaster. (Suppose an archaeologist comes across a big structure of a dead civilization. It looks like a tomb, and it's got "Warning: Horrible curse on all who enter!" written on it, and without understanding what it means, may lead to trouble). The Waste Isolation Pilot Plant project has been, for almost two decades, discussing with anthropologists and psychologists how to make it clear to people who may not even speak anything resembling our language thousands of years in the future that digging in the area will lead to mass amounts of death and suffering. They're well aware that whatever they do is going to be Schmuck Bait, and are taking steps to minimise it by making the entire thing instinctively look like somewhere you don't want to be.
Finally, Yucca Mountain has been abandoned for these very reasons. Deciding that we don't know how to seal the evil away for long enough, the official decision has been to seal it away in containers designed to last only 100 years, and let our descendants worry about re-sealing it. We are now officially Neglectful Precursors, unless it's Fridge Brilliance. A thing we have to reseal every hundred years is not going to be forgotten as easily. Like a story passed down from generation to generation, so long as it keeps getting told. Any disaster big enough to make us forget would be big enough that it probably wouldn't matter if the cache leaked.
An article was made on the whole language issue. The first thing that gets mentioned is that the current radioactivity symbol kinda looks like an angel from an ignorant's viewpoint. So... yeah. So just figuring out how to convey a complex concept as "invisible sciency-death" to potential aliens or post-english humans (or post-apocalypse cavemen) is a huge headache. This place is not a place of honor
Smallpox — live samples are kept in a couple places around the world.
Two places, officially: The CDC in the United States, and its Russian cousin VECTOR. Some Russian scientist have supplied information that may indicate the existance of smallpox elsewhere, however, making this particular can possibly opened.
The sarcophagus that currently entombs the exploded nuclear reactor at the Chernobyl power plant was built hastily and nobody intended it to be a long-term solution, so it quickly deteriorated and is presently in terrible shape. Yet it's still the only thing that separates the reactor structure, with all of its highly radioactive dust and materials, from the outside world.
They are building a bigger and better can around it Real Soon Now.
To be more specific, the Emperor had a scale model of (his) China built within his tomb. In place of water, historians wrote that the builders manufactured gallons upon gallons of mercury to be poured into the riverbeds and ocean, so that Shi Huangdi's sarcophagus, which was built as a dragonboat made out of copper, could sail around in for all eternity. That one can not enter the tomb without succumbing to deadly mercury vapors strongly supports the historians' accounts.
The Goiânia Accident: In 1987, a radiation therapy clinic in Brazil had relocated to a new office and had left behind one of their teletherapy machines — they've got into a legal dispute with a building's owners and received a court injunction forbidding them to take it to their new premises. The building was later partially demolished, but the machine was still intact in a remaining wing. Years later, two scavengers broke into the site looking for scrap metal to sell. They found the machine and broke it open, releasing the highly radioactive Cesium-137 from its lead container. The scrapyard owner who received the capsule from them mistook the glowing blue powder for carnival glitter; allowing children to play with it and spreading it around their homes and farms for good luck. The symptoms of radiation sickness were misdiagnosed as food poisoning. In total, 249 people were contaminated, with 129 suffering internal contamination from ingesting radioactive material. Four people died from whole body irradiation.
Any chronic health disorder that can be temporarily held at bay by medical treatment.
Pol Pot was placed under house arrest after being overthrown by his lieutenant and remained under house arrest for the rest of his life. Eddie Izzard has a really funny routine about it.
Eddie Izzard: So I suppose we're glad Pol Pot's under house arrest, I mean at least we know where he is; under house arrest, just don't go in that fucking house!
Augusto Pinochet also died under house arrest.
Quarantine procedures are designed to invoke this trope on contagious-disease vectors, toxic spills, and similar hazards.