666 Park Avenue: Whatever is in the Red Box that Shaw stole from Gavin.
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 Agents of S.H.I.E.L.D., the ancient Inhuman Hive is trapped on a distant planet so he cannot take over the Earth.
Many, many examples in Buffy the Vampire Slayer (the Judge, Acathla, the Seal of Danzalthar, among others) and Angel (Illyria [who is actually sealed in a coffin], 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. Cyvus Veil notes this of Sahjhan and cites it as a reason to kill him properly instead, jars can be broken. Pavayne and Sahjhan are also unique in that they are introduced free and are then sealed, as opposed to villains finding the sealed evil and seeking to release them.
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.
In "I Dream of Phoebe", the sisters find a Genie in a Bottle that's actually a demon who was sealed in the bottle and forced to act like a genie. If someone were to wish her free, she'd be unleashed and the person that wished her free would be forced to take her place in the bottle.
In season 7, when the Avatars attempt to remake the world, the demons decide that they've reached the Godzilla Threshold and break out rebel demon Zankou, who the former Source of All Evil (before the sisters vanquished him, or even existed) sealed in a can. One of the demons who goes to unseal him finds out firsthand exactly how dangerous Zankou actually is.
Chouseishin Gransazer: The last Bosquito was sealed on Earth in ruins left behind by the precursors, at least until Belzeus had it unsealed as part of his gambit.
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.
Dead Gorgeous: In "The Baharee", a box is opened containing a pipe or a horn. When Christine blows on it she unleashes a spirit called the Baharee which forces people to do things they wouldn't normally do.
Doctor Who: Around half a dozen cases of Evil deliberately Sealed in a Can. At least as many slumbering alien menaces that just happened to crash-land/get trapped centuries ago and go into hibernation until foolishly awoken, which don't technically fit the description but serve a very similar plot purpose.
In "The Tomb of the Cybermen", the titular monsters sealed themselves in a can figuring whoever could unseal it had abilities that would make the Cybermen stronger.
A slight variation happened in "The Stones of Blood", where the Doctor releases a pair of biomechanical judges called the Megara from a ship stranded in hyperspace, and the judges promptly sentence him to death for letting them free without the proper legal authorization.
"The Impossible Planet"/"The Satan Pit": A being known only as "the Beast" (who claims to be Satan) is so powerful it was sealed miles underground the surface of a planet precariously orbiting a black hole, meaning that any attempt to escape would send the Beast and the planet to fall into it. These Disciples of the Light guys really didn't want this thing to escape.
"Doomsday" features the Genesis Ark: a Time Lord device imprisoning millions of Daleks. "Time Lord science: it's Bigger on the Inside."
In "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.
"The Shakespeare Code": The Carrionites were sealed away a long time ago by the Eternals. Eventually, three manage to escape to 16th-century Earth and try to release the others. At the end, the entire species is re-sealed inside of a crystal, which the Doctor takes charge of to prevent them from being released again.
"The Waters of Mars" has Sealed Evil in a Glacier, specifically the Flood, which was deliberately frozen by the Ice Warriors. The humans who build a base atop the glacier don't realize there is any danger until a water filter fails, unleashing the Flood.
"The End of Time" implies that the Time Lock on the Last Great Time War could be this. With the sealed evil being the Daleks and the Time Lords (though it's more a Leaking Can of Evil for the Daleks since they keep finding ways to get out).
"The Day of the Doctor" indicates, however, that most of the Time Lords not on the High Council are not on board with Rassilon's megalomaniacal plan, which the Tenth Doctor already stopped, anyway.
In "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.
The Old God in the pyramid in "The Rings of Akhaten". It turns out the real Monster is the planet.
"The Witchfinders": The Morax were buried in Pendle Hill a very long time ago for war crimes, with a special alien tree serving as the lock of their prison. Then Becka Savage chops it down because it's obstructing her view... Fortunately, the Doctor is able to reseal the can at the end.
"Can You Hear Me?": Rakaya, the imprisoned woman in the orb, is actually an evil alien goddess and partner of Zellin. At the end, the Doctor is able to re-seal Rakaya inside the orb along with Zellin.
Forever Knight. LaCroix staked his vampire daughter Divia—who was too evil even for his standards—and sealed her in a sarcophagus in an Egyptian tomb. The seal of the sun disk of Ra kept her prisoner much like a Christian cross, until she was released by grave robbers and came after him in a Roaring Rampage of Revenge.
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.
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.
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...
The Kamen Rider series uses this in several series.
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 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.
Kamen Rider Revice has Giff, a demon sealed in some sort of casket. The villains of the season all want to revive him / harness his power for varying reasons.
Legends of Tomorrow: The Big Bad of Season 3 is the demon Mallus. Long ago, he nearly destroyed the world, until the six tribes of Zambesi combined the magics of their elemental totems to trap him in Another Dimension outside time itself. The plot of the season is driven by the cultists who serve him creating anachronisms in order to damage time enough that he can escape. This succeeds in the season's penultimate episode.
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.
Los Luchadores: One episode deals 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.
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.
Merlin (2008): The goblin from "Goblin's Gold", who was sealed in a box, then escaped to torment everyone in the castle, and then resealed after being trapped by Merlin and Gwen.
Midnight Mass (2021): The vampire remained imprisoned for an extremely long but otherwise unknown amount of time in a tomb near Damascus, kept sealed away by the tons of sand covering its prison and by its weakness to sunlight. That is, at least, until a sandstorm wipes away the layer of sand and the lost and confused Monsignor Paul stumbles into its lair...
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.
Ninja Turtles: The Next Mutation: The Dragon Lord and the Rank were imprisoned in an enchanted mirror until they took the opportunity to break free, menacing the Turtles and replacing the Shredder as the Big Bad.
The Outer Limits (1995): In "Abaddon", the crew of a ship in deep space discovers a hypersleep pod containing the body of a famous mass murdering warlord. He's let out and quickly begins to manipulate the people on the ship into killing each other.
Long ago, those Blackbloods who were belligerent towards humanity, and their Lu'quiri companions were tricked into entering the Plane of Ash by the more human friendly tribes, and then trapped there.
As first shown in the last scene of the Season 3 finale, and expanded on throughout Season 4, there's the Masters, the seven beings who inspired the Prime Order and Blackblood religions. Their bodies have been locked away for centuries in sarcophagi in hidden tombs, while their souls were separated in the form of the kinjs.
The Trope Namer 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:
Rita: Ahh! After 10,000 years I'm free! It's time to conquer Earth!
Her boss Lord Zedd eventually returns, and displeased with her failure puts her back in her dumpster (or a different one) and sends her off into space again. She gets out twice. The first time the Rangers catch her and reseal her, the second time she stays out for good.
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, Lothor, 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.
Double subverted, as Lothor is sealed in the Abyss at the end of the series, and then breaks out in the next season, Power Rangers: Dino Thunder, during the team-up episode.
In Power Rangers S.P.D. 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 Koragg'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).
The overall Big Bad of Mystic Force is a Lovecraftian monster who spends most of the series locked away, but still able to give orders to his subordinates.
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.
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 is one to the Nighloks, as nobody 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. The Big Bad, Master Xandred, gets an extra layer of this: he was sealed in the river by Jayden's father. Due to the seal being done wrong (which stems from the previous Red Ranger having insufficient power at the time), it causes him constant headaches.
"The Master Returns" shows, or at least implies, the nature of the seal: while in flashbacks set before the seal, he could previously leave the Sanzu River, when he personally takes the field in the present day for the first time, he immediately begins to dry out and is in agony every time the petrification spreads. After the battle, he remains at the bottom of the Sanzu River (so, not even able to command his forces from their ship that sails on it) until he can be fully restored for the final, season-ending two-episode showdown. It would seem the seal means he dries out much faster and more severely than a normal Nighlok and takes much longer to recover. The problem with this is that if he's willing to pay a very heavy price for five minutes of freedom, he could do unimaginable damage in those minutes, as the Rangers learned the hardway in that episode. Presumably, a completed seal would therefore mean he could never leave the Sanzu River without suffering an instantly fatal drying-out effect.
The Sporix in Power Rangers Dino Fury were captured by Zayto and Solon, but the two couldn't find a way to permanently destroy them. In the premier the chest containing them is opened during the fight between the Rangers and Void Knight, allowing them to escape. Even in the present, when the Monster of the Week is defeated, it simply returns to its egglike sealed form and must be returned to the containment unit, lest it hatch again (and we're told a Sporix is stronger every time it returns!) Interestingly, the Void Knight didn't mean to unleash them, and only wanted them so he could use their sealed form as a power source.
In The Sarah Jane Adventures, the race of supercomputers that Mr. Smith belongs to. Many of them are trapped within the Earth's crust, and Mr. Smith plots to destroy the planet to free them.
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.
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, seeing to it that it took him centuries to die. Damn. However, the Goa'uld are Puppeteer Parasites, 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.
Data's evil "brother" Lore in the Star Trek: The Next Generation episode "Datalore". He's found disassembled in Dr. Soong's lab and the Enterprise crew make the mistake of putting him back together.
The Star Trek: The Next Generation episode "Thine Own Self" plays off the Real Life example 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.
The Star Trek: Voyager episode "Alice" features an alien shuttlecraft that controls its pilots through its neural interface, appearing unto them as female avatars of their native species (as in the case of Abaddon and Tom Paris) and giving them brain hemorrhages to keep them in line.
This is 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.
Stranger Things: The can, in this case, is an alternate dimension with at least one but possibly multiple monsters inside it. Interestingly, there was never an apparent seal; the monster simply wasn't aware of our world. Until we became aware of it. Season 4 reveals that at least one evil from our world had been sealed by Eleven in the Upside Down.
The Stone Tape: The scientists investigating the Living Memory of a Screaming Woman imprinted into the stonework of a Haunted Castle accidentally 'erase' the scream. They give up their research, thinking they've blown their chance, and refuse to listen to the sole member of the team who insists the scream was 'recorded' on top of a more ancient evil, which is now free.
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. 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.
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. 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) "chomp the entire dish".
The end of Season 10 gives us the series' crowning example, as Death reveals that before the dawn of time itself, there existed only The Darkness, an amoral force of destruction. God and His archangels waged war on it and eventually sealed it away (allowing them to create the universe), creating the Mark of Cain to serve as its lock and key, though this resulted in the Mark turning into The Corruption for all who bear it. Freeing Dean from the Mark releases the Darkness on the world.
Lucifer is finally killed off at the end of season 13, flung into the primordial void where all dead angels go. However, in season 14 his former vessel Nick manages to wake him up and contact him in order to revive him. He's stopped at the last second by Jack, who then immolates Nick, but Lucifer is technically still out there, waiting...
Super Sentai, the source material for Power Rangers above, also has its fair share of examples.
Bandora in Kyōryū Sentai Zyuranger, the Japanese counterpart to Rita Repulsa above, is even named after the tale of Pandora's box. In her case, Bandora and her minions are sealed back at the end of her season and left adrift in space.
The Youkai are sealed away at the beginning of Ninja Sentai Kakuranger, having been trapped behind the Seal Door by the legendary ninjas Sarutobi Sasuke and Kirikagure Saizou. At least until two of their descendants unwittingly open it...
N Ma spends most of Mahou Sentai Magiranger locked away, though he can still give direct orders to his subordinates, who are working to revive him.
Juken Sentai Gekiranger, Jungle Fury's source material, also had the three sealed Kenma. In the series finale, after Long has pretty thoroughly backed up his claim to be immortal, the heroes do this to him, sealing him into a tiny sphere that Jan carries for safekeeping.
Deboss in Zyuden Sentai Kyoryuger starts the series off sealed away, and the scheme of the villains for much of the season is to revive him.
The first Torchwood season finale features Abaddon, son of the Beast who was sealed within the Cardiff Rift.
In Tracker (2001), Zin gets sealed in an underground vault during his attempt to steal the alien weapon hidden there.
The Twilight Zone (1959): In "The Howling Man", Brother Jerome tells David Ellington that the Brotherhood of Truth has had the Devil imprisoned in Wolfring Castle for the last five years and the world has therefore been spared his evil. Ellington does not believe Brother Jerome and releases the prisoner. Unfortunately, it turns out that he was telling the truth. Ellington spends more than 30 years attempting to atone for his mistake and recapture the Devil. He is eventually successful but a maid, who does not believe his claims, releases him.
Rod Serling: Ancient folk saying — you can catch the Devil, but you can't hold him long.
The Twilight Zone (1985): In "Crazy as a Soup Sandwich", Nino Lancaster uses a spell to shrink the demon Volkerps and trap him in a small box. He previously did the same thing to Volkerps' father.
Has appeared countless times in the Ultra Series. Some of the more notable cases include:
In the original Ultraman, two kaiju named Aboras and Banila were sealed away by a prehistoric civilization inside two separate canisters in the form of blue liquid and red liquid respectively. The monsters are freed near the episode's climax when the canisters' contents are electrified (by a scientific experiment for Aboras and lightning for Banila).
An episode of Ultraman 80 titled "The Mysterious Snow Art from Space" has UGM discover a strange snowflake-shaped object floating about in space that is brought to Earth to be displayed in a museum for its beauty. However, they soon learn that the object is in fact the prison of an evil entity called Devilon originally constructed by aliens - and luck has it that Devilon has just escaped and possessed Emi Jouno.
On Ultraman Dyna, one episode explains that the Nazca Lines are in fact the sealed cans for an army of monsters long ago brought to Earth by Ancient Astronauts. When said aliens are resurrected in the present, they manage to reawaken a bird-shaped one as the kaiju Dexador.
In Ultraman Mebius, Yapool's ultimate monster U-Killersaurus plays the role in The Movie, having been imprisoned by the Ultras in the seafloor off the coast of Kobe during the time between the series and the Showa era. The plot revolves a gang of aliens trying to awaken U-Killersaurus to use it as a weapon for galactic conquest.
Zaigorg, the Big Bad of the Ultraman X movie was imprisoned in an ancient temple centuries ago until a treasure hunter took the thing keeping him sealed away, thinking it was a priceless artifact, and accidentally set him free.
The King Demon Beasts of Ultraman Orb were all sealed away by different Ultra warriors in various locales, who then placed Cards of Power to act as locks.
Ultraman Taiga had Night Fang, who was imprisoned inside a mountain by a Shrine Maiden using the energy of the Earth itself. Said energy still resides within Night Fang when aliens release it from its prison, and it ends up giving Taiga his first Mid-Season Upgrade for the series.
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.
The Van Helsings also managed to imprison the First and Third Elders. The First, Abbadon, was locked away in a crypt hidden under a mountain (and which again can only be accessed by Van Helsing blood), while the Third, Abraham's twin brother Jacob, was sealed in a cage in a hidden chamber on a deserted island.
Warrior Nun: In the Season 1 finale, it's revealed that the angel Adriel is Buried Alive in a crypt in the necropolis under the Vatican. And that he's not the savior the nuns believe, having been imprisoned there to prevent him from conquering the world.
Willow: On their journey to the Immemorial City, Willow tells Boorman that the Wyrm is an ancient creature which feeds on magic (the very bloodstream of the universe) and it was imprisoned Beneath the Earth a long time ago, where it's still sleeping. The Crone worships the Wyrm and, it's strongly implied, wants it freed.
Wynonna Earp: The nature of the Earp Curse is that everyone Wyatt Earp ever killed has been raised as a demonic revenant. However, it also confines them within the boundaries of the Ghost River Triangle encapsulating the town of Purgatory and some of the surrounding countryside — if they try to leave, they begin to burn alive. Bobo's motivation throughout the first season is to try and find a way out for his kind.
Belshaar, the Widows' husband and Greater-Scope Villain of the series, was sealed at the same time, locked within a coffin, which was buried at the bottom of a mine, kept asleep by a trio of magic seals (which also created the barriers around the Ghost River Triangle as a side effect).
The Season 3 finale implies that the Garden of Eden is no longer a paradise, but a prison for something. The early episodes of Season 4 reveal that this entity is a shapeshifting demon who mockingly calls itself "Eve", who is kept locked inside a mystical barrier by a magitek machine powered by human blood.
