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In InuYasha, when Inuyasha obtains the red Tetsusaiga, an ability supposedly obtained by killing the guardian of the demon-bat caves, the guardian turns out to be a small half-demon child, Shiori, being forced to put a barrier around the caves. Inuyasha has to save her but won't kill her, at which she willingly gives him the ability by having him break open the crystal ball that created the barrier.
In Fractale, the world is maintained under a massive integrated system with a central program based off a human girl who, unbeknownst to the people who constructed the system, had been sexually abused by her father until she regressed to a childlike state. In order to refresh the system and prevent total breakdown, they need to not only clone said girl, they ultimately need to install that childlike personality into her as well as subjecting her to similar abuse, to make her as similar to the original as possible.
Magical Girl Lyrical Nanoha Striker S has the Saint's Cradle, a massively overpowered Cool Starship that can only power-up when commanded by a direct descendant of the Saint Kings of Ancient Belka. The problem? The last Saint King died over a hundred years ago without any heirs, so their bloodline is effectively extinct. So what is a Mad Scientist to do? Why, clone the last Kaiser, infuse said clone (despite her being a six year old girl, the one pictured above) with a Lost Logia, torture her until she is under his complete control, then make her activate the Cradle, despite how utterly painful the process is for her. The problem with that? Little Vivio just had to go and get herself adopted by not one, but twoAction Moms — both of whom qualify at this point in the series as People of Mass Destruction, and are less than happy with this Mad Scientist's shit.
In Mahou Sensei Negima!, as a child, Asuna Vesperina Theotanasia Entheofushia was an Artificial Human used to power the magic-cancelling defense system of Ostia while bound in chains. Later she was also used to power the magic-cancelling spell that would have destroyed the whole Magic World. Thanks to everyone's joint effort at containment, only the whole of Ostia was destroyed. The resulting mental trauma from being used as the power source to destroy a whole country was probably one of the reasons Nagi and party decided to wipe her memory and send her to Earth, so she could live a normal life as a schoolgirl named Asuna Kagurazaka.
In Katekyo Hitman Reborn!, the first generation of the Gola Mosca were powered by Dying Will Flames. As shown when Tsuna rips the Gola Mosca attacking Hibari and his friends apart and discovers a person inside of it. The situation is made worse for Tsuna since it was his grandfather', the 9th head of the Vongola family inside of it.
In Noein, the only thing protecting La'cryma from the encroachment of Shangri-la is a quantum computer powered by the humans embedded within it.
In Vision of EscaflowneAbridged, Emperor Donkirk became ruler of Zaibach by inventing a machine like this, one that turns blood into oil. As he put it "Cutting out the middle man"
The Record Of A Fallen Vampire: The Black Swan parasite inhabits teenage girls to kill the Strauss. If they can't, they are themselves killed by the Black Swan, usually in about 5 years. Also, the Black Swan itself was made from the souls of Stella and her and Strauss' unborn daughter. Really sad.
In the original Blue Drop manga, the Arume use their own children as bomb disposal units. They also use synthetic ones, but the "sacrifice" of the Arume children is more "beautiful" in the Arume's way of thinking—even though the synthetic children are full-blown sentient beings in their own right.
Most of Fullmetal Alchemist revolves around figuring out what makes the Human Resources work best, since live human beings are ingredients to creating certain powerful artifacts. It is eventually stated that the Amestrian Alchemy draws its power from human soul-energy provided by Father but the Xingese Purification Arts and Xerxes Alchemy are clean. As the series progresses it is revealed that Amestrian Alchemy really does derive from the Earth's energies as originally taught, but Father keeps a buffer that prevents alchemy's full usage and forces them to draw from the human soul-energy in his Philosopher's Stone. This conveniently gives him an "off switch" to every Amestrian's alchemy whenever he needs it. The Xingese were feeling this, by the way. More to the point, the human souls power (and create) the Philosopher's Stone.
This is different in the 2003 anime version, where it's revealed that alchemy instead draws its power from the souls of humans from a parallel universe— ours, in fact.
Galaxy Express 999 had the upper class using android bodies, powered by tiny energy cells that were made by harvesting humans.
Space Battleship Yamato 2199: The Cosmo Reverser System, sought after by the crew of the Yamato to reverse the destruction wrought on their planet, requires the memories of someone from the earth in order to work. The stored consciousness of Mamoru Kodai was originally meant to be used to facilitate this, but his spirit activated the system early so it could revive Yuki Mori for his brother, Susumu. When Captain Okita passes away shortly after the Yamato comes into range of Earth, though, his spirit restarts the system and saves the earth.
In Innocent Venus, artificially created children provide the neural systems in the mechas so that they are psychically compatible with the pilots. The memories of the trauma inflicted on them remain in the mechas, making it dangerous for pilots to stay psychically linked to their mechas for too long...
In Kurau Phantom Memory, human beings are deliberately afflicted with Rynax energy in an attempt to turn them into superweapons. Since Rynax energy consists of sentient beings, this procedure almost always causes a lot of misery for all involved test subjects.
In Mai-HiME, the summon monsters controlled by the HiME tied to the life force of their "most important person" (a family member, boyfriend/girlfriend, etc.). If that monster is destroyed in combat, the person dies with it and fades into the ether, also robbing the HiME of her abilities. This leaves a possibility that the killed character can be brought back to life, but this doesn't come into play until the very end.
Similarly, in Mai-Otome, the Otome usually can only use their robes after linking themselves to the life of a master.
Also, the dead body of Arika's Missing Mom Rena Sayers is the Predecessor of the Valkyries. Whether or not she was brought back to life and is merely in a comatose state is open for debate.
One episode of the Mini SeriesMAPS featured an orbital laser that was powered by the psychic energy released by hundreds of small animals being brutally killed en masse.
The titular cyborgs from Neon Genesis Evangelion are made from the cybernetically modified cloned flesh of the very beings they're used to fight and the souls of the mothers of the various pilots. And they're piloted by forsaken children, themselves, including a girl who is one of many clones of one of the aforementioned mothers (Rei), alongside that mother's son and the clone girl's sort-of half-brother (Shinji) and the daughter of another woman driven mad by an Eva-related experiment (Asuka)
Meta-example: Several of the crude images flashed up in End of Evangelion were drawn by abused children. Evangelion is itself powered by a forsaken child. It's that kind of show.
The lore has it that members of the Uchiha clan can only get the Mangekyo Sharingan by killing their best friend. Later events show that they "only" need the tragic death of a loved one, killed by them or not. But once you've done that, the fun really begins: using the Mangekyo Sharingan causes blindness and the only way to restore your vision permanently is to take the eyes of someone else who also possesses it, preferably a relative.
Kakashi's own Sharingan, which helped make him one of the most powerful shinobi around, was transplanted from his dying best friend Obito, a death Kakashi blames on himself. Kakashi and Obito/Tobi obtained the Mangekyo at the same time when Kakashi killed the Brainwashed and Crazy Rin, the partner whom both of them cared for.
Akatsuki member Kakuzu was able to obtain immortality by stealing his opponents' hearts.
Fellow Akatsuki member Sasori makes puppets out of people. And he's not the only one, either: it's a technique that was taught to him by his grandmother Chiyo.
Jugo can replace injured organs and body parts by absorbing those of other people. However, he's a nice enough guy that he restricts this to people who are already dead and even then only in emergencies.
Impure World Resurrection resurrects one dead person as an undying slave of the technique's user, at the cost of a live person used as a medium.
Soukou no Strain has the evil Deague searching for "samples", i.e. the mysterious alien Emilys. What they are samples of is the alien race that was dissected — without anaesthetic — to create the first mimics; the two Emilys in the series are the last living one and the last non-scrapped mimic with a still-living alien brain inside.
Serial Experiments Lain features a scientist who tried to tap the psychic energy of hundreds of children, apparently draining them and leaving them in a deep coma.
There seemed to be a some sort of explosion caused by an overflow of psychic energy, dissolving the children's bodies, trapping them forever in the Wired. The scientist comments how no matter what he does, bringing them back to real world is impossible.
In Vandread, the enemy's planet harvest organs to support themselves on a planet so polluted that they had to convert the entire surface into a giant machine. The enemy has gone as far as to manipulate the cultures of human colonies to cater to the harvest. The home world, Earth, has declared this necessary for continuation of humanity. All human colonies are just "parts" and are expected to fulfill their "purpose".
The bloody war between men and women in the protagonists' home system exists only to prime sexual dimorphism for the reaping.
A planet of telepaths have had a strong oral tradition until their vocal cords were stolen. They developed their ability to compensate.
In Witchblade the I-Weapons are corpses that had a cloneblade stuck on them.
Orbo, the fluid in Witch Hunter Robin that nullifies witchcraft, is later discovered as being made out of the drained bodily fluids of the witches everyone thought were being humanely imprisoned. Made especially horrifying, as many of the sometimes-innocent witches, including children, had character development earlier in the series.
There was also a witch whose power allowed him to sacrifice people to heal others. However, he only killed crooks, and eventually himself.
The Millennium Items in Yu-Gi-Oh! are revealed to be created with the souls of 99 slaughtered victims.
In the original Japanese version, they were created by literally mixing the flesh, blood, and bones of the victims into the gold used to cast them.
Also, the Duel Monsters used in the show are actually the souls of at least several citizens and soldiers from Ancient Egypt during Pharaoh Atem's rule, if not from billions of people in the anime's past.
Romeo X Juliet eventually reveals that Neo Verona's prosperity (and continued existence) is contingent on the willing sacrifice of the daughters of House Capulet, who become integrated with Escalus and bound to it for eternity. This does not sit well with Juliet's boyfriend Romeo, who fights first Juliet (the Sole Survivor of the Capulet clan) and then Ophelia (the guardian of Escalus itself) to save her from her cruel fate; in the end, however, Romeo dies right after defeating Ophelia, destroying Escalus in the process. Juliet then saves Neo Verona by turning herself into a new Escalus... but with the implication that the cycle of sacrifice that sustained Neo Verona in the past has finally been broken.
Gundam X featured, as a minor plot point in its ocean Story Arc, a group of pirates who use special radar systems made from the brains of dolphins. By the end of the arc the systems are destroyed.
Before this there was the MAN-003 Patulia, a Mobile Armor that required a Newtype (in this case, an Ill Boy artificial newtype named Caris Nautilus) to operate its wired beam cannons. Said newtype was rescued before the machine could consume him.
Let's not forget how another newtype ( an adult Girl in a Box named Lucille Lilliant) was sought after to force her lend her massive newtype powers to those who found her and her capsule. The Lorelei arc was focused on the Freeden crew finding said newtype first and saving her. They succeed, and Lucille is able to peacefully pass away after being 15 years in a forced coma.
All of these devices are predated by Victory Gundam's Angel Halo, a huge Zanscare fortress that contains a MASSIVE Mind Rape machine (basically, a whole fortress with psycommus all over), powered by 20.000 "physickers", all Newtypes who have been placed into capsules and put into constant trance to amplify the powers of a single Newtype (Queen Maria, and later her daughter Shakti); with it, the Zanscare Empire can collectively mindrape the whole population of Earth if they wish so. (Too bad that Shakti doubled as a Messianic Archetypeand the Spanner in the Works. Too bad for Zanscare, that is.)
You think that's bad? Try the Devil Gundum from Mobile Fighter G Gundam, where it was created to operate at it's strongest if a being that has the power to create life is its core. In other words, a woman. And unfortunately for Rain, she was the only woman around for the Big Bad to engage the final phase of his plan.
Come to think of it... every single Mobile Suit piloted by a Newtype or an Artificial Newtype can be seen as such, to different degrees. Double if it's an artificial Newtype, as these people are specifically trained and experimented on to acquire Psychic Powers at huge health and mental cost.
Another Gundam example would be the EXAM System from the Blue Destiny video game and related media. Accidentally created when something went wrong with attempt to make an anti-Newtype system, resulting in the consciousness and "soul" of the Newtype participating in the procedure being sealed within the machine...which apparently allowed it to be copied and split between the four EXAM computers built. The spirit of the trapped girl tries to communicate with the pilots, begging them to destroy EXAM so she can be at peace; Yuu Kajima agrees, while Nimbus Schterzen is convinced he's The Chosen One and wants to destroy every EXAM except the one in his machine.
The last use of this trope is seen in Gundam AGE, where a captured Yurin L'Ciel is strapped into the cockpit of a pink mobile suit and used as an amplifier for Desil's powers. It ends as well as expected.
In the non-canon crossover between Mobile Suit Gundam ZZ and Space Runaway Ideon, Neo Zeon planned to use seven-year-old Princess Mineva Lao Zabi and her Newtype powers to reawaken Ideon. All it did was piss off the mecha and force Amuro Ray and Judau Ashta to save her and put it down.
Project ARMS. Pretty much literally. Almost every Egrigori experiment uses a child as the test subject. Most prominent are the Keith clones which were implanted with the first ARMS, many of which turned into monsters as a result, the Chapel children who were given drugs while in the womb to make them super smart and work as scientists for the group, various mutant and psychic children taken to be soldiers, and Alice who was on the research team and whose dying body was bonded to an alien lifeform and became a computer controlling the Egrigori. There's also the other ARMS teens, who were specially genetically engineered to be soldiers to take down the Egrigori.
The magic in the parallel worldcomes from the lives of the people from the normal world.
It is revealed that the daughter of Gray's teacher, Ur had too much magic energy in her body, which was making her ill, because of her naturally high level of magic energy she was taken away and experimented on (her mother believed her to be dead, while she believed her mother abandon her.) It's not completely clear whether Ultear was just experimented on or if her magical energy was somehow being used to power the facility)
Elfen Lied has Number 28 and the vector tank. The less said about how they operate, the better you'll sleep at night.
In Bokurano, the energy that fuels the Humongous Mecha is the Life Energy of the pilot. Meaning, whoever pilots it to save the world will die immediately after the fight is over.
Moreover, it's theorized (and strongly implied) that the younger you are, the more Life Energy you have. Which is offered as an explanation for why it's preferable for teenagers and little kids to fight and die in huge terrifying mecha battles, even when they join up with the army, and have access to combat-trained volunteers - it certainly explains why Koyemshi is so adamant into having Kana Ushiro, the youngest of the group at age 10, to pilot it. The world of Bokurano is such a nice place, isn't it?
The Reverse Explosion system in 009-1, which is powered up by the Psychic Link between the mutants in the world, many of them just being children. Mylene, the titular 009-1 agent, decides to go rogue to stop it.
An episode of Betterman reveals that an "unmanned" mech is actually piloted by another character's "dead" baby brother - now effectively a Brain in a Jar. Releasing him really does kill him.
A short film called Hide and Seek had kids being hunted by demons through an empty city, and when they were caught, they were plugged into a generator just like every other group of children to play the game before them, presumably so the lights would lure more children to come and play.
RahXephon. The huge mecha style beings attacking the city are in fact psychically linked to people within the city. Thus when the being is damaged so is the person they're linked to. There is a rather interesting plot twist in that a young girl who's in love with the protagonist and whom he swore to protect... turns out to be one of those people and he ends up killing her, while believing that he's protecting her. Cue very unterstandable angst when this happens.
Junior◊, from Read or Die the TV appears first as a mysterious, effeminate child antagonist, working as a secret agent for the British Library towards their heinous goal. He's lived a lonely life, and is automatically drawn to those that show him kindness. However, after his Heel-Face Turn it becomes apparent that Junior was kidnapped as a baby from his I-jinn mother (Nancy) and had basically been his entire life to become a vessel for The Gentleman. The process involves having all the old man's information DOWNLOADED into his brain. And ... what's supposed to happen to him? Um, you don't want to know.
In Bleach, Aizen nonchalantly reveals that he fed his Hogyoku with souls of Hollows and Shinigami alike. He implies this is one of the few ways to awaken it/make it evolve. One of his victims was actually a pre-teen Rangiku Matsumoto, who had a good part of her soul stolen to power it up. Also Hollows like to eat human children or hollow children as much as anything else.
In the Battle of the Planets episode 'The Space Beetles', the title mechas were powered by kidnapped children. Making the premise even MORE evil than the Science Ninja Team Gatchaman episode it was derived from (which simply used children's destructive instincts to direct the mechas).
But they still retained the children inside them, making them effective hostages.
The G-Force: Guardians of Space version had the beetles powered by the destructive impulses -and Gallactor was going to turn the four boys into Brains in Jars to make things 'simpler'.
In the Sailor Moon Super S movie, Queen Badiane wanted to use all of the children on Earth like this, kidnapping them and putting them on stasis to feed off their dreams.
In the Kikaider OVA series, an enormous doomsday device requires Dr. Gill's son to power it.
Played literally in 2004 horror OVA Kakurenbo. Abducted children are used as a power source for the whole city.
In Magic Knight Rayearth, many characters, including the heroines of the story, have come to regard the Pillar system as one.
Yuui and Fay in Tsubasa Reservoir Chronicle}}, in an Omelas-esque fashion. Since the people of their country believe that twins inherently bring misfortune to those around them, it's decided that the two kids should be sent to the Sinners' Valley, a hellish limbo of sorts, so this doesn't happen. It doesn't work.
Pasifica Cassul in ScrappedPrincess may be considered this seeing as she was basically a nuke for the Church, she was meant to gather energy her whole life, and then die on her 16th birthday, releasing the energy and defeating God in order to set the world straight.
In the last post-Zero Hour volume of DC's Legion of Super-Heroes, there was a new galaxy-level faster-than-light spaceship drive introduced by the government of the United Planets. The Legion discovered that the drive power sources were living and sentient beings who had been created by the government via the abduction, torture, and genetic splicing of citizens of two of the United Planets' member worlds - and that being used to power the drives put them through agonizing pain and slowly killed them.
A Marvel Comics crossover storyline had the villainous Secret Empire capture mutants to drain their greater-than-normal psychic energy to power weapons and vehicles to take over the U.S.
The events are later revisited in the short prose story "Firm Commitments", told from the point of view of a scientist who discovers the immense thermodynamics-breaking potential of Mutant neurons, gets involved with events far greater than himself, and has his life ruined as a result.
Doctor Doom permanently sealed his position as truly evil rather than arrogant Well-Intentioned Extremist when he tracked down his first love, convinced her he had abandoned his technology and evil ways, then sacrificed her to demons in order to boost his magic powers as a complement to his genius tech. The demons then gave him a cloak made from her flesh, which he wore.
During the Messiah War X-Men storyline, an alternate future version of Kiden Nixon is used by Stryfe to empower a machine that prevents time-travelling.
In Elseworld's Finest: Supergirl & Batgirl, there is no Superman or Batman; the most powerful superheroes are their Distaff Counterparts, Supergirl and Batgirl. Batgirl is trying to take down Lex Luthor, and elicits a reluctant Supergirl's help. They both travel deep underground Metropolis, trying to find the 'clean fuel source' that Lex Luthor discovered for the city years ago. It turns out that it's her cousin Kal-El...who never got to grow up, but died as an infant in a jar. But considering that this is Lex Luthor, are we truly surprised he'd stoop so low?
The power rings of the death worshipping Black Lantern Corps of Blackest Night don't rely on emotions like the others. Instead they are powered by killing a lot of people. Killing a person and stealing their heart restores 0.01% power to every ring in the Corps. So it takes about 10,000 hearts to recharge all the rings to maximum power, minus the power used to steal those hearts of course. And when all the rings are charged to 100%, Nekronappears.
Speaking of which, it's common knowledge that the rings of Green Lanterns and other similar corps run on emotions, but the Lights Out arc revealed the dirty little secret that they're finite power sources. Once those emotions dry up, the universe ends - and this isn't the first time it's happened.
Blue Mountain, home of the Gliders in Elfquest, featured doors and ornaments that were maintained and controlled by rock shaper elves. Once free-willed elves, these rock shapers were so deeply sunken into meditation or mental numbness that they were oblivious to all but other Gliders' commands to open or close.
Frau Totenkinder of Fables sacrificed her own child in exchange for her considerable magical powers. In order to keep said powers, she also has to sacrifice one newborn every year. In modern times she has supposedly stopped killing infants and uses donated blood from newborn Fables instead. It's heavily implied that she also maintains her magic by working at an abortion clinic.
Actually, some of the text from that part implies she owns at least one abortion clinic, and generates power from that. And considering that this is NYC, imagine how many she ends up sacrificing and how much extra power that gives her. Here's a hint - In Queens alone there are almost 20,000 a year, and only 10 places to get them.
As Frau Totenkinder's encounters with Hansel and Gretel (shown in flashbacks) indicate, in a pinch a child of any age will do. Kay's comments also indicates that Totenkinder sacrifices hundreds, possibly thousands, of children, upon which the old witch says she 'invests her money in perfectly legal ways among the Mundy'.
The Iron Man miniseries Hypervelocity reveals that the AI used for Life Model Decoys and elsewhere in the Marvel Universe — such as the Virtual Ghost backup of Tony Stark who's the series' protagonist — was based on horrific human experimentation. The bad guys in the series are the Virtual Ghosts of some of the test subjects.
Iron Heights, the horrendous supervillain prison for the enemies of The Flash, is powered by Fallout, a man who was irradiated and accidentally killed his family. He is so irradiated that he needs to be quarantined so that his energy can be safely released. When the Flash first sees him, the process for powering the prison is extremely painful. He later makes the warden change the system so that Fallout is more comfortable.
This is oddly similar to The Dark Knight Strikes Again, where Flash himself is used to power an entire city by essentially running on a giant hamster wheel all day, every day.
In an obvious shoutout to The Matrix, Archie Comics' Sonic the Hedgehog features a new creation by Dr. Eggman/Robotnik after the Roboticizer is rendered obsolete: the Egg Grape Chambers. Eggman captures Mobians in them and uses their life force for power. This slowly drains their memory as well. Left too long, they can be killed, or at the very least left with amnesia of varying degrees.
The use of someone's life force for energy is also the principle behind the energy weapons and rockets built into Bunnie's robotic limbs. One enemy (the Iron Queen), who usurped control of her robotics, tried to use this to kill her via overexertion.
In the Mystique comic, there's a mutant who can control all machines and gets plugged into a giant device that requires her power to run. She's a little girl, of course.
DC Comics: The Reign In Hell miniseries reveals one of the more feared punishments of hell was becoming building materials.
Incorruptible. The Superman analogue goes quite insane after a living entity spreads itself by turning kids into skeleton zombies. 'Supes' caused this by negligence. Oops.
In Mark Waid's Empire, Golgoth has Endymion(essentially this Universe's Superman) hooked up to a machine that drains his blood and turns it into a hyper-addictive drug
Give Me Liberty has secret experiments performed with schizophrenic kids. One of them turns out to be a telepath.
A plot point in Teen Titans had Deathstroke's team breaking up a drug manufacturing ring that created Bliss, a drug literally made from children. It's later revealed that the reason for Roy Harper's behavior while supposedly on heroin (supposedly in that there was no way a man on heroin would be able to fight like he was) was that Deathstroke was secretly spiking his heroin with samples of Bliss.
Checkmate: In a story arc involving the Suicide Squad, the team is shown invading a power plant in a Southeast Asian dictatorship. A boy emitting solar power is hooked up to a machine siphoning the energy. They break him out, but leave him in the Mirror Dimension, on orders to make sure he is no longer a threat to American interests.
In the 2008 Guardians of the Galaxy series, the alien Universal Church of Truth powers its technology with "Belief Engines", generators that draw on the faith of its legion of worshippers. At least one of their starships is shown carrying storage banks full of the faithful, kept in stasis and wired directly into the ship's power systems.
The X-Men storyline that introduced the Brood established that the Brood's ships are made of the Acanti, huge alien life forms that float around space. The Brood capture them, lobotomize them and turn them into living vessels powered by pain.
During the "Home Schooling" arc of Runaways, when an injured Klara Prast accidentally raises a massive forest around their house, Nico and Karolina struggle to convince Victor and Chase to leave it alone, because they're afraid that the forest might be connected to Klara's own lifeforce, and therefore attacking it might cause her even further injury.
A story in Heavy Metal Magazine depicted a disparate group of beings infiltrating and fighting their way through a high-tech structure, eventually reaching a computer resembling a huge, sleeping human face. They blasted open a dome on the forehead and remove...a baby. The only text is at the end, over panels of the group walking in a garden-like setting, in the style of an intelligence report on the destruction of the City of Om, caused by the failure of the central computer system known as The Dreamer, due to the removal of the "human component" known as "The Soul of The Dreamer", who is now "enjoying the ecstasy of life."
Aeon Natum Engel has a Patrone system being both using and used by Special Services sorcerers.
In the Pony POV Series, Fluttershy, upon learning how cruel the world can be, finds a source of powerful magic and sets out to turn Equestria into a perfect utopia by siphoning out all vices, sadness and wickedness of the world... using herself as container to hold them. She decides to bear all the evils of Equestria upon her back, and suffer eternally herself just so no one else has to ever suffer anymore. This also ends upgrotesquely deforming her. She even refers to herself as the Forsaken Foal of Omelas.
In Rainbow Factory, rainbows are made out of foals who fail their flight exam. Specifically, their ribs are broken, and then they are mutilated in what is essentially a giant meat grinder.
The sequel, Pegasus Device, makes it worse by mentioning that the victims must be fully conscious, because the fear and pain is an integral part of the process.
The Powers Of Harmony: Zemblaini sacrificed Horizon — a two-year-old foal — in order to use the innocence of his Lifeforce to force open the Gates of Tartarus and release Nightmare Moon's army. Celestia managed to link his remaining Lifeforce with the Echoes, stablizing him and keeping the Gates sealed. However, he's remained trapped there for the twenty years since, awaiting the day the Elements of Harmony are restored and used to undo the damage. And part of his mind is still aware...
The Dashverse story Hot Heads, Cold Hearts and Nerves of Steel starts with Sombra's minions kidnapping every foal in Ponyville and several other towns. Several chapters later, when said minions confront the Mane Six, they reveal that the reason the foals were taken was so Sombra can sacrifice them to empower himself.
In the Tarnished Silver series, Princess Celestia convinces herself (on scant to nonexistent evidence) that this is how Equestria works, so she sets out to clandestinely shield pedosadist slaver rings from justice such that an adequate population of forsaken children will be maintained.
When you learn that Dante is the doctor in the AU Fullmetal Alchemist fanfiction Asylum, you can tell that this trope will be in effect.... In this universe, Philosopher's Stones can be fueled by alchemic energy, but you can't get enough unless it's pushed through an alchemically potent human, or 'conduit.' If done in excess, this process will eventually turn the conduit into a Soulless Shell. Of course, Dante doesn't care much.
In Harry Potter and the Soul Gems a dark wizard used large diamonds containing the souls of children with special abilities to power the traps which protected the tombs he built for his clients.
In Episode 67 of Sonic X: Dark Chaos, Eggman and Rouge discover the truth behind Beelzebub's fake Chaos Emeralds; they're empowered by Dark Chaos Energy - produced by dozens of lobotomized slaves undergoing And I Must Scream.
Film - Animated
In Monsters, Inc., the entire monster society is powered by the screams of children. Later on, we get introduced to the Scream Extractor, which fits this trope even better by sucking out the screams of a single kidnapped child in order to gain more power. Thankfully it never gets put into mass use, and in the end the monsters find a better power source - popping out of closets and making kids laugh instead of scream.
In Tangled Mother Gothel uses Rapunzel's magical hair, which she inherits from a magic flower, to stay young and beautiful. She does this through kidnapping Rapunzel, tricking her into believing Gothel is her real mother and manipulating her into staying in a tower her entire life.
In Pinocchio, boys are turned into donkeys and sold to saltmines, or end up working in circuses, on farms, or are made to pull the wagon that brings more boys to Pleasure Island.
There's a more mundane/clueless example in ParaNorman; the town of Blithe's Hollow depends on attracting tourists and selling them things based off of a witch-hanging done three hundred years ago. The witch is revealed to have been an eleven-year-old girl who was killed for being weird. It's only incidental that her ghost is sticking around, furious and unable to move on.
Film - Live Action
According to Warlock, one of the ingredients of a flying potion is the rendered fat of an unbaptised child. While in modern times there are alternatives that are not fatal to the child, the character is from the 17th century, back when there were no alternatives, and kills the child extracting it. The potion is based on a (supposed) actual witches recipe of the era ("fat of unbaptised brat" even gets a mention in Shakespeare). Likewise the nail in the footprint has a real world source.
In the movie Daybreakers, most of the remaining 5% of humanity has become this, as the 95% vampire population needs human blood to survive. People are kept in storage, barely alive, and have their blood drained via tubes to feed the vampires.
Arcade features a video arcade named "Dante's Inferno", where a new virtual reality arcade game called, boringly enough, "Arcade" is being tested. If you lose, you're trapped inside the game and die. Turns out the game is Powered by a Forsaken Child.
The boy was abused and, eventually, killed by his mother. The game designers decide it's a good idea to take a few thousand brain cells from the body and use them in the game.
Apparently, the game is somehow able to transcend virtual reality and enter Real Life. At first, it can only grab people who are in the arcade booth. Then, the game is ported to consoles, and the game is able to do the same thing in people's homes. At the end of the film, it looks like the boy projects himself on the street, meaning the game is becoming more powerful.
In The Animatrix it also becomes Fridge Horror when you realize this is Humanity's fault as well: The Machines originally ran off mostly solar power until some geniuses created the eternal night to try and shut them down for good. The Machines simply got creative and ironically green in their quest for alternate energy sources.
In Thir13en Ghosts the ghosts of the title are used to power some sort of demonic machine designed to open "the eye of hell".
Minority Report has a pretty literal version: the Precrime department's method of predicting the future involves three psychics, kept in chemically-induced dream state 24-7 and hooked up to a computer, so that the detectives can piece together visions of murders from their recorded dreams. Where does literal come into it? Well, it turns out that the Precogs are actually the abandoned, mutated offspring of drug addicts. Doubly frightening was the knowledge that one of the creators of the Precrime system was willing to kill the mother of one of the Precogs to ensure that they would stay Forsaken Children.
X-Men has the machine that turns ordinary people into mutants powered by Magneto—but using it weakens the power source (likely killing him if he uses it on full power), so he forcibly has the power-stealing mutant Rogue absorb him and uses her to power the machine.
In the original draft for the movie, Magneto actually wanted to use Wolverine instead as a sort-of living antenna to amplify his powers, apparently due to his Adamantium skeleton.
And in X2: X-Men United, Stryker's mind-control serum is derived from chemicals secreted by the brain of his own son, Jason; though still alive and still capable of using his impressive powers of illusion, Jason's been given a lobotomy to make him more pliable and is confined to a wheelchair- complete with a shunt in the back of his head used for collecting the fluid.
And in X-Men: The Last Stand, the mutant cure is distilled from Leech's blood, though they hope to eventually artificially synthesize it. Unlike other examples, Leech is treated rather well and seems fine with the arrangement.
Film/Snowpiercer At the beginning we see lower class children measured and taken away. At the end we find out that they're used as manual labor within the train's engine to replace broken parts.
Revelation Space - The brains of children are installed in the Conjoiner Drivers according to Reynold's short story "Weather as found in Galactic North. Their minds do a bunch of math that lets the drives work. Something of a subversion to the trope as the Conjoiners consider running a drive to be a vocation which is chosen voluntarily. The brain can decide to be reintegrated with a body after working for a few decades.
In Steel, by Carrie Vaughn, the villain crafted a sword by quenching it in the blood of his own daughter.
Actively defied in-universe in the The Ship Who series, which features starships that are run by deformed children encased in electronic "shells" since infancy: Only children born with untreatable disabilities whose quality of life would otherwise be very low are chosen for the process, they receive a pretty good salary and if they earn enough money they have the option of buying out their assigned ship and becoming freelance. (Buy-outs are expensive but attainable, especially given how long shellpeople live.) Most of the "shellpersons" we meet are happy enough with this arrangement; it may not be ideal in some ways, but there are worse alternatives.
In Black House by Stephen King and Peter Straub, the "Big Combination" is a gigantic city-machine powered by the slave labor of abducted children, and their collective screaming can be heard over the roar of the machinery from miles away.
From outside comes the clank of the Big Combination and the screams of the children who march, march, march on their bleeding footsies, running it.
The Wamphyri in the Necroscope series use humans to build their warships, chthuluesque warbeasts, homes, plumbing, etc.
David Mitchell's Cloud Atlas contains a sinister example.
David Drake has two separate examples in one book, in Cross the Stars:
A settlement of Kettleman Bubble houses, which are luxury dwellings that can produce anything the people in it ask for, and use anything organic (but non-human) as raw material. The problem arises because Kettleman was a raving racist bigot who had a very narrow definition of "human" — it didn't include Italians, for instance...
The Alayan space drive, which is based on warping the perception of objective reality in a sentient mind, eventually driving the "fuel" mad and useless.
"Any sentient mind will serve the purpose," said the Alayan. "Any mind with a grasp of reality and the ability to change reality through fantasy, if you will. We direct the fantasies so that they become real . . . and the vessel moves in objective reality through the pressure of the subject's mind. Unfortunately, that mind moves as well, in a psychic dimension from which it cannot be retrieved. We could use ourselves as subjects, but we do not do so while we have minds aboard which are not ours. That is the main value for which we trade."
In Mike Carey's Felix Castor series, the Satanist Church of the Americas, under the command of Anton Fanke, create "sacrifice farms" in order to have a regular supply of forsaken children for precisely this purpose.
In Vernor Vinge's A Deepness in the Sky, the Emergents' society is driven by the Focused; people who have had their brains reconfigured to make them obsessed with a certain subject, making them super-competent at that but unable to function in anything else, putting them in a sort of intellectual slavery. One of the main characters envisions using this to create the kind of orderly interstellar empire that, due to a lack of Faster-Than-Light Travel, has always fallen in the past, but in the end, realizes the human cost is too much.
In The Gone-Away World by Nick Harkaway, the world has been polluted by "Stuff" which responds unpredictably to human thought. Normal life is only possible in the neighborhood of a pipeline that pumps out the counter-agent, called FOX. The main character eventually learns that FOX is created by exposing stuff to the minds of people who have certain very specific brain injuries, which almost inevitably lead to their rapid death. The brain injuries are specific enough that the corporation running the pipeline has to abduct people and inflict the injuries themselves in order to insure a sufficient supply of FOX.
Using the blood of a unicorn can keep you alive, but you have to kill a unicorn to get it. This also curses you for life, although the specifics of this curse are never explained; Firenze simply refers to it as a "half-life, a cursed life". Voldemort only uses it as a stop-gap on the way to his true goal.
The spell that restores Voldemort to full power requires the bones of his dead father, the flesh of a servant (Wormtail's hand) and the blood of an enemy (Harry).
Using a Horcrux to store your soul requires murdering someone, and splits your own soul apart, leaving the other part in the Horcrux.
In His Dark Materials we find out in the last book that the Spectres (intangible soul eating wraiths and the series' Eldritch Abominations) are actually made by using the subtle knife. Much to the horror of of Will who has used the knife countless times since he obtained it.
A more direct example from The Golden Compass was cut from the movie version: Lord Asriel was required to kill a child in order to power the Applied Phlebotinum (as a death by separating a child from their daemon unleashes energy on par with nuclear fission), and much to Lyra's horror, the boy happened to be one of her friends. She spends the better part of the The Amber Spyglass going To Hell and Back to try to make up for it.
That scene was still filmed and can be see on YouTube. It gives us the chilling line from Lord Asriel, "The life of one child does not matter. Not when freedom is at stake."
This is also one of the plots of the The Illuminatus! Trilogy, where many of the aging higher members of the Illuminati intend to become transcendentally Illuminated, that is, immortal disembodied spirit-beings, by using a carefully-honed piece of rock music played by four of the five Illuminati Primi to reanimate a legion of SS stormtroopers sunk at the bottom of Lake Totenkopf in Bavaria by Hitler - also an Illuminatus - as a secret weapon. The old second world war era Nazi zombie superweapon will be used to kill the thousands of people attending a huge concert, so that the energy released by their slaughter can be absorbed by the illuminati and used to achieve immortality. They're stopped when Sex awakens the goddess Eris whose apple of Discord throws the zombie Nazis into disarray, and they are finished off by the porpoise allies of the Discordian leader. Yeah, it's an odd book.
Being the chessmasters that they are, the four Illuminati Primi also have two other backup plans to achieve the same thing, should their primary plan fail: one involves magically inspiring the creation of, then stealing and releasing a powerful biological weapon known as "Anthrax Leprosy Mu"; the other is intended to trigger a nuclear war between the US, USSR, and PRC by creating a three-way Bay of Pigs-style escalation of the Cold War in a small African nation.
Literal in Tamora Pierce's Protector of the Small series. The killing devices are powered by the souls of murdered children. The devices are killed by opening the head, which is when a small, white, ghostly form comes out and blows away, sometimes asking for its mother or crying. Sometimes the killing device itself will ask "Mama?"
It's said that the mage who makes the devices doesn't need to use the souls of children. He just likes to.
In Venus on the Half-Shell by Kilgore Trout (Philip Jose Farmer, NOT Kurt Vonnegut), the interstellar drive works by painfully draining the Life Energy from beings in another universe. The faster you went, the louder the wailing you heard coming from the engines. At the end of the novel, the last being dies, ending interstellar travel permanently.
In The Dark Tower's Wolves of the Calla, it's revealed that the bad guys' captive psychics are being fed a substance to boost their powers. That substance is withdrawn from the brains of kidnapped twin children, one from each pair, leaving them mentally slow, unnaturally big and doomed to die young.
Dracula — and most other vampires since him — have to drain the blood, or life force depending on variation, of living people just to survive.
Lightbringer, Azor Ahai's sword from A Song of Ice and Fire, which the smith tempered by plunging it into the heart of his beloved, killing her horribly.
Most major magic in the Ice and Fire universe seems to have some element of this: a repeated statement is that "only death can pay for life" when performing blood magic. That includes draining the life force from unborn children, burning people of "a king's blood" alive, and less deadly examples, such as taking the faces off dead people in order to magically assume their identities.
Employees of The Pilo Family Circus are paid in bags of mysterious powder that, when melted down and drunk, can grant wishes. It's later revealed that every grain of this powder was once part of a human soul, extracted from the Circus' audience.
Subverted by Alastair Reynolds in the short story Weather. Conjoiner drives include living, thinking human brains as an integral component, to calculate reaction pathways—but Conjoiners consider this a high honor and an enjoyable experience (so long as the drive's working right.) It's something akin to a challenging video game.
Myrddraal swords in the Wheel of Time gain their exceptionally lethal properties from an exceptionally unpleasant process. After being quenched in a black river that would be lethal even to the rock golems that make them, they're finished off with a human soul. They are implied to require regular "topping up."
In the Otherland series, the network is quite literally powered by a forsaken child. And not the whole thing either. Just his brain and its incredibly strong Psychic Powers.
In The Black Wind, a novel by F. Paul Wilson, the titular "Kuroi Kaze" or "Black Wind," a hideous black cloud that kills all living things, is powered by a child's death. Preferably a "mixed heritage" child (i.e. a child of mixed race.)
In the Myst novel The Book of D'ni, the beautiful realm of Terahnee is secretly sustained by the ceaseless labors of millions of mind-numbed slaves, kept out of sight in underground warrens. Atrus is horrified to learn his own innocent request that an entertainment device be run at high speed has killed dozens of men and women, worked to death to power an apparatus he'd assumed was engine-powered.
More precisely, it was another member of his expedition, Marrim, who made the request.
In the Nightside, Forsaken Children are fairly standard-issue sources of power for villains. In Nightingale's Lament, for example, John Taylor discovers that the Nightside's electrical grid is running off energies from a murdered man's spirit, who'd had solar powers in life. As he'd also been a close friend of John's, Taylor sets the spirit free, blacking out most of the Nightside. Passing references to ambulances powered by human pain are used simply to set the mood of the neighborhood.
In the opening sequence of Just Another Judgement Day, Dr. Frankenstein uses counterparts from another dimension to provide the local party people with eternal youth through an arrangement similar to Dorian Gray's.
In Timothy Zahn's Deadman Switch, a planetary system is discovered that's full of extremely valuable minerals, but there's a field around it that shuts off FTL travel, so there's no practical way to get in. Unless, as it turns out, you have a freshly dead corpse in the navigator's seat. No, this doesn't cause people to write the place off, don't be silly. They just start using convicted criminals.
It's slightly more disturbing when you realize the other consequences, like the fact that the initial research team only got there because while investigating the "cloud" their navigator had a fatal heart attack, or and once they figured it out, they had to draw straws for who would die so they could make the return trip.
Nor is that the only time that's happened, when a ship lost the second criminal they were going to kill to get out. It's also implied that the central government is doing all it can to insure a large and continuous supply of death-penalty convicts, even convicting people who don't deserve it.
In Interworld by Neil Gaiman and Michael Reaves, the ships used by HEX and the Binary to move between worlds is powered by the life essence of captured Walkers. At least in the case of HEX, they first boil away all unnecessary parts, such as your body - while keeping you magically alive through the entire process.
In The Sword of Truth books, in order to get into the world of the dead and back alive, you had to (minus the incantations): 1) brainwash a young boy into complete loyalty. 2) Kill him by making him drink molten lead. 3) Cook, mash and eat his brain, heart and testicles. 4) use the boy's spirit to travel there and back again - and woe if the boy's spirit doesn't remain loyal all the way through...
In David Farland's The Runelords series, anyone can acquire magical upgrades to their senses, strength, intelligence, speed and so forth with magical "endowments." The catch? Endowments don't create ability, they just transfer it from one person to another. So you can have the strength of two men, but in order to provide it there's got to be another man lying in a bed somewhere who's too weak to even raise his own arm because all his strength is being funneled to you. To receive an endowment of wit (intelligence) is to literally convert someone else's brain into an extension of yours. Now consider that nobles often have dozens of endowments...
In the Mithgar books, a mage literally has to give of their own soul to work their magic, causing them to age dramatically (though they can then go into stasis for extended periods to recover lost youth). Black Mages, on the other hand, find this process cumbersome and inconvenient, so they power their magic with other people's souls, generally wrenched from them through acts of tremendous mental and physical cruelty. As this process is implied to become somewhat addictive, there's a reason most Black Mages end up insane.
In American Gods we encounter one small Midwestern town with none of the problems of young the folk moving away and aging populace and unemployment, crime, and drugs that plague the region. Wanna know what the town's guardian god has to do to keep Lakeside the "one good town in these parts"? Three guesses, and the first two don't count. Child sacrifice. Somewhat averting the full trope, none of the townspeople actually knew of this, and considered the missing children to be lost and perished in the woods, or 'winter runanways'. Anyone who figured it out had an unfortunate 'accident' before they could tell.
Not only that, but hundreds of years ago Hinzelmann, the town's protective deity, was himself a child sacrifice by and for his tribe. He achieved his godhood by being raised in complete darkness, never knowing light or love, till one night when he was six he was taken out, pierced by swords, and his body smoked over a fire. The sacrifice he extracted for his continued protection of the town was one child every winter.
In Simon R. Green's Deathstalker series, the Darkvoid Device turns out to be one of these... powered by Giles' own son.
In the Vorkosigan Saga by Lois McMaster Bujold, there is House Bharaputra, a clan/business on the disreputable world of Jackson's Whole. They specialise in cloning and genetic engineering, and most notably provide a rejuvenation program for the very rich: clone them, brainwash the clones so they won't fight it, then transplant the brain of the original into the clone.
In the Gemma Doyle Trilogy, someone without power of her own can get a warped version of it by performing a sacrifice. This is what Sarah Rees-Toome/Circe and Mary Dowd/Virginia Doyle try unsuccessfully to do to Carolina, what Felicity almost does to a deer, and what Pippa does to Wendy's rabbit, Wendy (unsuccessfully), and Sahira/Mrs. Mc Cleethy. This is either part of the reason for her corruption or a result of it.
In the Secret Histories series by Simon R. Green, specifically in The Man With the Golden Torc, Edwin Drood uncovers his family's greatest secret: each Drood's magical armor was created through the sacrifice of his or her twin sibling as a baby.
In The Laundry Series by Charles Stross, many of the Laundry's weapons are made this way. Standard issue Hands of Glory are sourced from political prisoners in China (they tried using chimpanzees for a while, but there was less bang for the buck and animal rights activists got involved). The construction of the Violin that Kills Monsters required the torture and murder of twelve innocent people. (They investigate the feasibility of making more like it, but "Just owning the necessary supplies probably puts you in breach of the Human Tissues Act of 2004, not to mention a raft of other legislation.") The ritual for binding the Humanoid Abomination codenamed TEAPOT calls for the blood of babies.
It says a lot about the tone of the Laundry's setting that some positive examples of this exist. Ungern-Sternberg, for instance, constructed something called the "Wall of Pain" from the undead, crucified bodies of war prisoners in order to create a quantum-observer effect that would prevent the Sleeper in the Pyramid on the Dead Plateau from rising.
All of the above are actually the protagonists' tools. What the bad guys get their powers from...
Then there's what happens to the young, virginal (in one case 3 year old) riders of Unicorns...
In the Chanters of Tremaris trilogy, the Palace of Cobwebs, a beautiful and delicate structure that looks like it's, well, made of cobwebs, is the home of the Emperor of Merithuros and his court. Unbeknownst to its inhabitants, the Palace cannot actually stand and must be continually chanted into being, day and night, by five children, all of which have had their legs broken and never set properly so they are unable to escape.
In C.S. Friedman's Magister Trilogy, magic is harnessed by making use of one's life force. While normal witches wind up prematurely aging and dying while still relatively young because of this, the Magisters themselves figured out a workaround for it. Simply put, they link themselves to the life force of some complete stranger elsewhere in the world. The mere mortals have no idea that they're being used by the Magisters, believing that people who are linked in such a way are suffering from some horrible disease that even a Magister is not able to cure. Needless to say, fledgling Magisters have been hunted down and killed by their teachers in order to keep that little fact a secret.
Many forms of Black Magic in The Dresden Files rely on torture and death to power them, with the Darkhallow in Dead Beat being perhaps the most extreme. It involves the sorcerer killing enormous numbers of people (in this case, the entire population of Chicago) with necromantic energy, then consuming all the ghosts in the area to achieve godlike power.
The heroine in Lynn Flewelling's Tamir Trilogy is hidden from a King Herod style massacre of the innocents by a Gender Bender spell powered by sacrificing her twin brother at birth, an act of necromancy so horrific it has consequences that last for years and eventually causes all of the witting participants to meet untimely and grisly deaths.
In Warbreaker, all magic is powered by breath. Each person has one breath, the loss of which saps creativity, harms the immune system, and can lead to mild depression. People can voluntarily give their breath to others, so poor people often sell theirs to the rich. Most magic takes upwards of 20 breaths to accomplish, and some people have more than several hundred. The "gods" of the series, the Returned, each need to consume one breath per week or they die. The donor is often a child since their breaths are considered better than that of the elderly.
From Mistborn by the same author, Hemalurgy, one of the three core magic systems, works on this principle. Its use involves trapping a portion of someone's soul in a metal spike and then sticking the spike into someone else, endowing the recipient with superhuman abilities via the stolen life-force (what, exactly, is transferred depends on the kind of metal the spike is made of and where it's placed on the recipient's body). Oh, and so far as we know, it's not possible to do this without it being fatal to the unfortunate "donor".
In John D. MacDonald's Ballroom of the Skies, the galactic government deliberately keeps Earth impoverished and war-torn ... because that toughens Earthpeople spiritually to the point that they make good recruits to run the galactic government.
One Animorphs book has a controller who's discovered a way to avoid returning to the pool every three days. He eats his fellow Yeerks, killing lots of human controllers to get them.
In Devon Monk's Allie Beckstrom novel Magic on the Storm, Shame finds the nursery the hardest part of the hospital — all that life that could be drawn upon. Allie is relieved that he assures her he wouldn't, because she would fight him over it, and she doesn't want to fight him.
In the MR James story "Lost Hearts", Mr Abney has cut out the hearts of two homeless children he took in, as a ritual to give himself eternal youth. He plans to do the same to his own orphaned nephew to complete the ritual, but the ghosts of the first two children get to him first.
In The Acts of Caine book Heroes Die, Ma'elKoth spends the life of his devotees when using combat magic. Unlike most, he is aware of the cost; when he gives Berne a smidgen of that power to use, he reminds the man of the human cost, and he uses this fact against Pallas Ril.
Blood Lotus from Stormdancer, first book of The Lotus War. In order to keep fields from being rendered unusable after two or three years, a fertilizer made of mammilian blood must be used. Now that most forms of animal life have been driven extinct, prisoners of war are used.
Animating the dead in The Witch Watch requires taking the life force of a human. Magical healing requires it as well
In Chris Bohjalian's The Night Strangers, the tincture that adds decades to your life requires blood from a "traumatized" twin child. It's not supposed to be Human Sacrifice, but the ritual works out that way both times the users try it.
At the climax of Tad Williams's Otherland, it is revealed that the simulated world most of the story takes place in is created by the child of one of the main characters, who is a telepath.
The system of magic in Dave Duncan'sA Man of His Word series (and the follow-on series A Handful of Men) is based on "magic words". The words are not used to cast spells, simply knowing them gives magical power, and each word increases that power — up to four. The hero, Rap, at the beginning of the series knows one magic word: his long and complex True Name, of which "Rap" is an extremely shortened form. Partway through the series, it is revealed that the magic words are the True Names of Fairies, who are tortured to force them to reveal them after which they die. Rap and his companions also accidentally discover that if someone who actually knows what his own heart's true desire is meets a fairy, the fairy is compelled to reveal its True Name to him — and die.
There's also a contingency plan in case a powerful group of magicians appears — use the above described technique to quickly create enough sorcerers to beat them.
The process of "artificing" in Glory in the Thunder involves taking a human soul and giving it an artificial body. For the less scrupulous practitioners, forsaken children are the easiest souls to come by...
This one is Older Than Radio. In The Brothers Karamazov, Ivan uses a thought experiment as a metaphor for the problem of suffering. He asks his brother Alyosha, a novice monk, if he would create a world of peace and happiness for everyone, under the condition that he has to torture one child to death. Alyosha says no.
In the Paradox Trilogy, humanity was facing potential annihilation from Eldritch Abominations called phantoms. An alien race, the lelgis, taught humans how to create weapons effective against the phantoms — but only at a terrible cost. Plasmex-sensitive children are kidnapped from their homes and are transformed into "daughters", powerful psychics capable of killing phantoms. Daughters only survive a few years before going insane and dying, and protecting all of humanity's many colony worlds thus requires a steady stream of human sacrifices.
Live Action TV
Stargate SG-1 had tretonin, a drug that granted the user perfect health-but had a side effect: the drug destroys the immune system, rendering the user dependent on the drug forever. The SG-1 team, after beginning negotiation for some of the drug, learn that the drug is actually created from the offspring of a Goa'uld queen the Pangarans discovered in a stasis jar. Normally this would not be so bad considering the Goa'uld are the series' Big Bad, parasites that force their way into humans' brains and take over their bodies while most likely applying eternal mental torture to the host mind. Unfortunately, much later, after the Tok'ra (the rebel faction of the Goa'uld who were allies with Earth) are brought to help analyze the drug, it is discovered the Goa'uld queen is actually the Tokra's long lost queen (and their last hope of reproducing as their number are dwindling and she was the only known Tok'ra queen). Naturally the Tok'ra object to such treatment of their queen.
Eventually subverted when, later that season, the Tok'ra are able to synthesize tretonin without the need for live symbiotes.
Because said Tok'ra queen showed them how before dying.
One episode featured an immortality drug that required killing people to manufacture it. The Vorlons decide We Are Not Ready for immortality and assassinate its war criminal creator before she is able to pass on the formula.
The Shadows use living beings, suitably adjusted, as the control units for their spacecraft. They also use people to grow some of their technology, according to one of the canon novels. It's not stated whether this kills the people on whom the stuff is growing or not, but it's not a pleasant process.
Babylon 5 also contained the alien healing device, which can cure any wound or illness but only by siphoning life energy away from a healthy being (its creators used it as a means of "just" capital punishment, taking their life to insure somebody else got to keep theirs).
The Buffy the Vampire Slayer episode "Doublemeat Palace" leads the viewer to believe Buffy has encountered a Soylent Green-type situation — only to move on to a more realistically plausible, but equally strange-feeling twist.
The Season 8 comics have Buffy's new bonus powers. Subverted, as she soon finds out her power, like all magic, came from the Seed Of Wonder. As she got closer to it, she bacame more powerful.
The First Slayer herself is essentially a forsaken child forcibly infused with demon energy by magicians. Essentially true of all slayers.
Dawn is this for Glory in Season 5, with the blood of The Key being required to open a portal that Glory needs to return to her home dimension.
Cleopatra 2525's robotic oppressors of humanity were revealed to be slightly less robotic than believed: They're cyborgs, using brains harvested from human children.
HBO aired Cosmic Slop, three short supernatural stories hosted by George Clinton. One story was about a fleet of aliens arriving to earth and offering to solve all of the world's current problems. In return for all of the people of African descent who do not pass the 'paper bag test'. Did they get their price? In a heartbeat!
In the sadly-lost story The Savages, the inhabitants of a technologically-advanced city extended their productivity and lifespans by draining "life force" from the people who lived outside the city. While they admittedly tried not to take enough to kill anybody, it was more because they didn't want to lose their supply than for humanitarian reasons.
In "Revelation of the Daleks", Dalek creator Davros offers to help solve a galactic famine problem. How convenient that he's set up shop on a cemetery planet...
In "Remembrance of the Daleks", a young girl is kidnapped and mind-controlled to augment the Supreme Dalek's rational and logical battle computer with human imagination and emotion.
Played with in Silence in the Library/Forest of the Dead: the library's computers are run by a terminally-ill child who was inserted into the mainframe to keep her alive and entertained with every book in the universe. Powered-by, but hardly forsaken.
The Toclafane in The Sound of Drums / Last of the Time Lords, who the Master uses as his personal army of Happy Fun Balls, can be considered part of this trope. Martha Jones pries one of them open and discovers, to her horror, that the Toclafane were created from the final remnants of humanity. Instead of traveling to the fabled Utopia, they end up in the reaches of space, gradually turning on each other, cannibalizing their own bodies, and becoming more childlike.
"The Girl in the Fireplace" has a spaceship that uses stolen body parts from its crew to replace its broken parts.
The Controller in "Bad Wolf", a Wetware CPU wired into the Deadly Game space station—although she's an adult when we see her, one of the minor characters explains she was "installed" when she was five years old.
She's also the only one who knows about the villain and their evil plan, but she can't say anything about it until a coincidental solar flare cuts her off from their control.
In "The Beast Below", the Starship UK is propelled by torturing a Space Whale. No, really. And in a "The Ones Who Walk Away from Omelas" parallel, every citizen of Starship UK is told just what their megaship relies on for power at age 16 as part of the "elections." They are then given the choice to Forget or Protest; most choose to Forget via Laser-Guided Amnesia, whereas those who Protest end up food for the Whale.
Also subverted in that the Space Whale purposefully came to help because it heard the crying children of England and wanted to save them. The humans of course has no way of knowing this and thus captured and tortured the whale to propel the ship, not knowing it would've helped of its own free will.
House, from "The Doctor's Wife". By extension, its servants Aunt and Uncle.
There's also the hospital on New Earth that has the cure to every known disease...and it finds these cures by experimenting on human Expendable Clones.
Classic Who, Fourth Doctor, "Warriors' Gate": Rorvik's culture has spaceflight dependent on wiring a time-sensitive slave into the navigation systems and hitting that slave with high voltages.
The way Torchwood fights back is literally this trope, they re-route the Four-Five-Six's psychic Mind Rape wave back at them through a forsaken child. Specifically Jack's grandson Stephen who was the only child near when the solution was discovered with minutes left to save the day. Stephen screamed himself to death.
In Heroes, the Big Bad of the first season, Sylar, is capable of "acquiring" the superpowers of others through an unshown (until the beginning of season 3) procedure that requires killing them and removing their brains.
Technically he doesn't have to kill them to do it as he learned in volume 3. However the quickest route to it is studying the brain and (Unless the victim has a healing factor) the process of slicing their head open is shown to be fatal.
It's implied in a later volume that he knew even before volume 3 he could absorb powers through empathy. He just liked knowing every little thing about the power, and the life of the person who had it meant little to him.
Sakurai Yuuto, aka Zeronos in Kamen Rider Den-O has people around him lose their memories of his future self every time he transforms. When that turns out to be insufficient, then he gets his new Zero Form, which is powered by peoples' memories of his current self (this after nearly disappearing completely after his past self is killed by an Imagin). In the end, the future Sakurai does disappear completely... leaving the current Yuuto with a different, new future to discover.
The first season of Lexx, also known as "Tales from a Parallel Universe", was made up of four movies. The second movie, "Eating Pattern", revolved around a junkyard planet where bodies could be made into a highly addictive drug called "Pattern". The title Living Ship also eats planets, occasionally including inhabited ones.
Let alone growing the Lexx in the first place; prisoners from all over human space (most of whom had only committed fairly minor offences) had their major organs cut out by circular saw (to make robotic drones, apparently?) and the rest of their body was shrinkwrapped and fed to the Lexx. All it has to say on the matter was that "The food was good there".
And even later, the entire population of the League of 20,000 Planets received the same treatment; becoming food for the Gigashadow, the body of the last survivor of the Insect Civilization.
The Otherworld episode "Paradise Lost" had a immortality drug called Kaloma that was created by draining the life force of human beings.
In an episode of Masters of Horror entitled "The Fair-Haired Child", the plot involves a grieving couple appealing to an otherworldly force to resurrect their dead son. They in turn, have to feed him ten children. The child shows his um...gratitude to them in a similar way.
In an episode of The Invisible Man, an eminent neurologist is removing pieces of homeless people's brains in order to cure those he considers more worthy who've suffered brain injuries.
He gets proper justice in the end - he falls off the stairs to his death. Since he's an organ donor, his own brain serves to cure one of his victims.
In one episode of Sliders, the characters stumble upon a village with its own Fountain of Youth. Which is the excretions of a gigantic mutant worm...whose primary diet is people.
An episode of The Worst Witch has Sybill turning a torch into a magic lamp that will grant any wish. The catch is however that it'll absorb energy from other things to grant each wish. When it runs out of plants to absorb, it starts to drain the girls and the teachers instead.
In Battlestar Galactica (Reimagined), President Roslin's cancer is cured by injecting her with the blood of Helo and Sharon's unborn daughter. Thankfully, they don't need all of it.
The source of the treatment is in fact scheduled to be terminated, but the efficacy of the treatment means that she gets a stay of execution. There's no actual risk from the small amount of blood extracted. It's more a case of Powered By An Unharmed Child.
An episode of First Wave had Cade stumble upon a Gua-run hospital, where they were helping some people... by giving them parts from other people's bodies. None of this was altruism, of course, but merely just another experiment.
There is a (disputed) theory that the final verses of the children's song "London Bridge is Falling Down" relate to pagan use of human sacrifice during construction of important buildings.
In Big Finish Doctor Who "The Genocide Machine", it is revealed that in the Library of Kar-Charrat the Chief Librarion Elgin has captured many of a local aquatic life form and placed them in a wetworks facility so they can be used to download data, a process which destroys their minds.
Magic The Gathering has a whole color based on this principle: Black. The whole concept of black mana is sacrifice for selfish, personal gain — even to the point of sacrificing bits of yourself. All colors have some sort of ubercard that's cheap to use but has some drawback. Black, however, is the king of this, with a hideous number of cards that allow one to do quite a lot of awesome things, but cost you creatures, land, life, cards in hand, cards in graveyard (a viable resource for black, so not something to be sneezed at), or something else. One makes you lose the game if you don't win by the end of your next turn.
Not to forget that black's ways of regaining life generally involve taking it from others, as per the classic Drain Life spell...
The infamous Necropotence allows the player to trade life for more magical power and knowledge (i.e. draw cards). One common combo is creature removal (i.e. killing creatures), discard spells, and the Avatar of Woe, a huge creature which costs eight mana (two of which have to be black), but only costs the two black mana if there are a total of ten or more creatures in all graveyards. This card was so powerful it has been banned or restricted in most formats.
Years before Necropotence was the Ur-example of self-sacrificing cards: Lich.
Another notable early example was Lord of the Pit, an extremely powerful creature for its cost that requires a sacrifice of one creature per turn or it turns on you.
In the game's backstory, Urza collapsed Serra's Realm, killing everyone inside, to activate the powerstone core of the skyship Weatherlight. Also, during the Invasion block, when Urza led a group of planeswalkers into Phyrexia to destroy it, he powered the bombs he planned to use with the soul of the planeswalker he expected to betray them. Which was justified, in that he was right.
Paranoia has this when you ask what the incredibly Dystopian society is eating. Depending on the version, it's everybody who dies, or everybody who dies who wasn't Blue rank or above. Including children. (Or just bland things like algae and synthetic protein, but even then, people accidentally falling into food vats is disturbingly common.)
All Arcane (non-Badass Normal) powers in Deadlands work this way. The setting has it as an explicit rule. The soul involved is inevitably your own.
Except for Blessed and Shaman powers, which only require adherence to your religion and (in Shamans' case) proper rites. You still do the sacrifice, but it's voluntary and only involves limiting yourself.
While not known in Deadlands: The Weird West, it is common knowledge in the Wasted West that ghostrock is made up of souls, which scream and wail as you burn it.
A few creatures such as demiliches can trap souls and fuel spells with these.
In the Dark Sun setting, use of arcane magic, by default, drains life force from the environment around you, killing plants and leaving the soil infertile for years. Widespread use of such magic led to the world of Athas becoming a desert wasteland. Magic users who embrace this are called Defilers; those who learn to use magic without harming the environment are called Preservers. The respective advantages and drawbacks of Defiling vs. Preserving varies from edition to edition. In second edition, Preservers advanced in power more slowly than Defilers. In fourth edition, Defilers can drain life force from their own allies to empower their magic.
The creation of permanent enchantments in AD&D2 involved the decrease of the Constitution attribute. The Forgotten Realms (Volo's Guide to All Things Magical) has the 'Blood Link' spell, which allows the vitality of another sentient creature instead of the caster's own to be sacrificed for permanency (though this could compromise alignment, like most lifeforce-draining effects). Which also explained how drow and Red Wizards got tons of magic trinkets.
Vhaerun grants a spell allowing the caster to drain levels (lifeforce) for use as charges for magic items.
Continued in later editions, with slight modifications. In Third Edition, permanent magic item creation requires spending XP. Note that XP and levels in this game represent life-force: many vampires and similar creatures literally drain your levels when they feed.
Mystara has a nuclear reactor of some crashed spaceship that became a magical power source, with some training allowing its users to try a divine ascension. Those who fail the attempt are sucked inside and become more fuel. Later, its acidentally ascended original operator made a copy free of other (worse) side effects.
Too many examples in Ravenloft to mention them all; perhaps the nastiest was Azalin's Doomsday Device, powered by the stolen souls of his murdered enemies and the collective life forces of every living thing in Il Aluk, greatest city in the game setting. Also featured in Dance of the Dead, a Ravenloft novel, in the form of an enchanted riverboat powered by captive fey and magical beasts.
Spelljammer had the Lifejammer helm, a magical device that allowed ships to travel through space by draining the life energy of creatures placed within it. Death Helm is the same with Charm effect, so the victim who failed a saving throw will fight off attempts to pull them out of this.
The Book of Vile Darkness supplement features a foe called the Dread Emperor who uses this trope. He wears special golden armor that has four small children attached to it by lengths of chain. When hurt he can drain life from the children to heal himself. Players wishing to take him down (and who wouldn't?) must find a way to deal with this or risk sacrificing four innocent lives in the process.
The book also includes the Soul Eater prestige class, which allows the player to gain strength and abilities by bestowing negative levels on their enemies, essentially draining their life force. The player can eventually take their victim's appearance and all of their abilities if they kill someone this way.
In the Warhammer 40,000 universe, the Imperium of Man has the Astronomican, a giant psychic beacon essential for warp travel. Originally powered by the Emperor's immense psychic strength, the device is later powered by the souls of ten thousand psykers (daily) trained for the purpose. The Astronomican's extreme psychic energy requirements cause the psykers' deterioration and death in only a few months. A constant stream of sacrificial psykers is therefore required to power the Astronomican.
Although at least the psykers who power the Astronomican are trained, and see the giving of their lives as their last and greatest duty. A similar process of soul-draining is used to feed the Emperor, and their compliance is... not so neccessary.
It's also implied that the longevity treatments that allow even Puny Humans with enough wealth or ranking to live for a few centuries are made from children. Even sympathetic and otherwise heroic characters are known to use them, just to show how fucked up the setting is.
Depends on which type of juvenat treatment it is: they apparently range from synthetic/cybernetic organ replacements and plastic surgery through to (implied) fetal stem-cell therapies. There is one variant noted in the early fluff which involved cloning a person, applying some phlebotinum to cut-and-paste said person's soul into the clone, then spending a couple of decades (re-)teaching it skills and brainwashing it to think it was the original. Sure, it runs afoul of the Continuity Problem, destroys the soul of an innocent and wasted 20 years back in school, but hey, what with the other treatments out there, this body's good for another 2-3 centuries or so...
In addition to preying on humans to sustain themselves, the vampires of Vampire: The Masquerade can perform diablerie - feeding on their elders to improve their generational status.
Then again, their elders tend to be homicidal maniacs, stark raving crazy or complete monsters. And of course, every vampire's afraid of the day the Antediluvians, the Elders among elder vampires, are going to rise again, eat every last one of their children and generally be bad for the neighborhood. So, killing older vampires is a "sacrifice" that many younglings are willing to make. As soon as possible.
In Genius The Transgression, materials like these are called Larvae. They constitute any item which invoked an Obligation roll to obtain, and offer increases to efficiency. Earlier editions followed up the section on Larvae with the quote from Doctor Orpheus at the top of the page.
In Werewolf: The Apocalypse, most supernatural items known as Fetishes (no, not that kind) are powered by a spirit that's permanently bound into the item. While most werewolves prefer to strike a voluntary bargain with a spirit, others may skip the "voluntary" part...
Characters in Mage: The Ascension with enough skill in the Spirit sphere could do the same thing and were considerably more likely to substitute coercion or brute force for diplomacy.
Since Vampire: The Requiem (Masquerade's reboot) doesn't have the concept of 'generation', it handles eating other vampires differently: if you chow down on someone more powerful, it boosts the power of your blood, expanding your capabilities. Sufficiently potent vampires, however, end up needing to feed on other vampires to survive.
Speaking of Vampire: The Requiem, there's a Trope Codifier for this trope in the form of the Belial's Brood faction known as the Mercy Seat. They are based on gnosticism and believe that the world is evil. It is possible to leave this evil world and reach a higher realm of existence, but in order to do so, they must basically damn someone to hell in order to rectify a cosmic imbalance. The more innocent the sacrifice was, the better the chances of leaving this world. Allegedly. The fact that there's a bunch of evidence, both in mechanics and fluff, to back their assertions up is another trope.
In Mage: The Ascension, it was possible to extract quintessence (the energy that makes reality real) from the life force of a willing creature. Many mages use their own life force. Some use specially reared livestock. A few villains use specially raised children. (A larger number of villains will attempt to use unwilling sacrifices, but this creates enough "resonance" opposed to the intended effect that it cancels out any potential benefit. They either don't notice, or don't care.)
And, as in Ascension before it, a mage can gain mana from sacrifice. Most sacrifice their life force or their physical capabilities (both eventually get restored), but they can also sacrifice other living creatures. Trouble is, to do so they have to kill the victim - and humans give more mana than animals.
In Wraith The Oblivion, the spirits of the dead — which would include the characters — can be boiled down and forged into anything from furniture to money. If that weren't bad enough, the unfortunate victims used to make this "soulsteel" remain conscious, and those who carry soulsteel items can occasionally hear them weeping.
In Exalted, the magical material known as Soulsteel is...well, filled with the aware, agonizing souls of the imprisoned dead (not surprisingly, Wraith was a big influence on Exalted's Underworld).
And Starmetal is made out of the bodies of (usually) minor gods, although in this case the gods in question are not conscious (with one non-painful exception).
Perhaps the most literal case in the setting is the phylactery-womb, the device that the Yozis use as the staging point and storage device for Infernal Exaltations. Her name used to be Liliun once, and she was a daughter of the Scarlet Empress, traded over as part of mommy's botched deal for immortality. Now she's been twisted and violated in a number of senses, left barely lucid and babbling, just so that she can serve as the perfect receptacle for the Infernal shards.
There is also the 'Mephitic Engine of Desolation', a necromantic device that prevents prayers from reaching gods and the heavens. It's created by the ritual torture and sacrifice of five children... Suffice to say, the details are unpleasant.
In the GURPS "Madness Dossier" setting, the heroes are fighting alien monstrosities who seek to destroy all of human history in order to restore their own, in which humanity is a Slave Race. To do this, the heroes adopt and adapt the enemies' psychological weapons — which tends to make them act more and more like the enemy. Also, the more people know what's going on, the greater the chance that the enemy will win. So the heroes have to use mind control, amnesia-inducing drugs, propaganda, and when all else fails, old-fashioned murder to keep humanity in ignorance.
In BioShock 1, the Plasmids are marvels of superscience that give powers from generating electricity, to telekinesis, to shooting swarms of angry wasps from your arm, through genetic engineering far ahead of their time — or our time. But to obtain ADAM, the Applied Phlebotinum needed to make new plasmids, sea slugs have to be implanted into little girls — it must be little girls, for reasons that are never explained.
Tenenbaum: I know why it has to be children, but why just girls? This I cannot determine why, but I know it is so. Fontaine says, "Ah, one less bathroom to build in the orphanage".
At some point shortly before the beginning of the game, a plasmid has been developed that will allow someone to destroy the sea slug from within, yielding a considerably lesser amount of usable ADAM but rendering the girl a normal human being again. In most cases.
In most versions of Dwarf Fortress, dwarves will occasionally enter a "Fell Mood" - leading them to kill a nearby dwarf, process his carcass in the nearest Butcher's Shop, and turn it into an artifact. This being Dwarf Fortress, nine times out of ten it's something like a dwarf-bone scepter decorated with an image of a dwarf-bone scepter in dwarf leather.
... adorned with hanging rings of dwarf bone and menacing with spikes of dwarf bone.
Also, this being Dwarf Fortress, the other dwarfs don't freak out when one of their number starts murdering people. It's more a case of "Hey, what a neat scepter!"
To the point where tons of engravings, sewn images, et al. will be made to celebrate the creation of this fine dwarf bone scepter. Again, this being Dwarf Fortress...
Heroic spirits in Fate/stay night agree to fight in the Grail Wars because they believe it will grant them a wish, usually to let them live a second life or fix a past mistake. However, a defeated Servant is actually drawn into the Grail where it is turned into pure magical energy, and the 'winning' Servant that touches the Grail is also subject to this. This is what powers the Grail. Only the last remaining Master really gets a wish. However, very few of the main characters actually know this while competing, possibly only Ilya and Zouken Matou.
All the Servants participating in the holy grail wars, except Arthuria, are actually spiritual 'copies' created from the immortal concept of the hero, which exists beyond time and will remain inviolate no matter what happens to the copies. The same hero can therefore potentially participate in any number of Grail Wars, as it's only the copy that's absorbed. It's still pretty ghastly, though; copies or no, they're still sentient beings.
Doubly ghastly when you consider that the spoilered part must be the fate of Miyu Edelfelt Emiya in any universe except the one in the spin-off Fate/kaleid liner PRISMA☆ILLYA.
Final Fantasy IV's Dark Knight Cecil and the Fake King have a few shadows of this. The former's Dark Knight Armor is aparently powered by Cecil's own Spirit (it actually reduces the stat), while the King's first mission is to destroy a town to gain power.
Final Fantasy V's Job Crystals are a subversion. They do contain the souls of the Light Warriors who first defeated Enuo, but they willingly grant the heroes their power so they can stop Exdeath.
Additionally, the final Guardian Force, Eden, has an ability called Devour, which enables Eden's host to eat his or her opponent in order to gain various benefits from HP to stat increases - although depending on the opponent, the effect could be negative instead. Either way, the game cheerfully acknowledges the rather Squicky implications of this: the animation for the ability involves cutting to a screenshot of a serene landscape, over which is played the very loud, messy slurping and smacking noises of the target being messily eaten. Bwahahaha.
Final Fantasy IX has Quina the Blue Mage. To learn blue magic spells, s/he has to eat the enemy. His/her weapon? An oversized fork. Additionally, the fuel everybody uses to power airships, Mist, is made of souls barred from the afterlife, but it's never made quite clear whether they're actually consumed in the process.
Each summonable creature in Final Fantasy X is powered by a different Fayth, a person willingly entombed in crystal specifically for that purpose. Look at the lovingly rendered temple wall decorations incorporating the body of the sacrificed Summoner.They're◊ really◊ quite◊ lovely◊. You don't even notice the protruding parts of the entombed human body unless you look closely! Somebody put real care and artistic vision into those, which is morbid beyond belief when looked at in this context.
The Fayth are on call for the summoners at all times; whether they're pulled from their slumber every time a summoner needs help, or deprived of rest completely like those on Mt. Gagazet, it sounds like a pretty miserable way to pass the centuries.
Final Fantasy X-2's Dresspheres are created from memories of past people, in fact Yuna being overcome by the memory of the Songstress Sphere is a major plot point. Now keep in mind there are about 40 of these dressspheres, most of them created by Shinra 'during' gameplay. However, Lenne sealed herself in the songstress dressphere entirely by choice, and can clearly leave anytime she wants; she's just waiting for Shuyin to be saved before she does. The person who's memories are recorded in the Black Mage dressphere is met by the player and clearly not trapped.
In Final Fantasy XI, learning blue magic involves "absorbing" the "essences" of monsters. Translate the euphemisms yourself. Furthermore, it's dangerous to do this, as a blue mage grows gradually less human as they gain more spells. It's implied that any character who actually does pursue the path of blue magic is amoral and ambitious. It is revealed that at the end of their life they transform into soulflayers.
It's true that the Aht Urhgan Immortals, a sect of Blue Mages who've sworn their eternal servitude to the Empress, become Soulflayers when they die—but after the Blue Mage LB 5 fight, it's strongly implied that because adventurers live a completely different lifestyle according to completely different ideals, their will is strong enough to fight the Beast indefinitely.
Scholars too. The Grimoire—the source of a Scholar's power and versatility—only achieves its true power after several rituals. The first one? Soaking it in the blood of other magic users—especially other Scholars.
In Final Fantasy XIII, the fal'Cie Orphan powers the entirety of Cocoon, especially the antigravity tech that keeps it from falling onto Pulse. Of course, this gets more complicated when you find out that most of the game has been orchestrated by Barthandelus (possibly under Orphan's influence, depending on interpretation) just to get you to kill Orphan, destroying Cocoon and killing millions of people in the hope that the Maker will return to the humans and fal'Cie alike, who are seen as having been forsaken by him.
Wasn't the entire point that the Fal'cie of both cocoon and Pulse were working together, pretty much raising the cocoon population for the mass sacrifice, and that the entire plot is them trying to do it again since the chosen pulse L'cie didn't do the job 400 years previous?
In Final Fantasy Adventure and it's remake the Mana Tree that sustains the world will grant it's power to the first person who touches it and then die. The only way to save the balance of nature is for a woman of the Mana tribe to become a new tree in it's place, a fate that befell the heroine's mother and eventually the heroine herself.
This appears pretty often in Heroes of Might and Magic V. The Necropolis Town has a building that can convert living units into Undead. There's an adventure map building where a Hero can sacrifice units in exchange for experience. The Demon Lord Heroes' "Consume Corpse" ability removes dead creature stacks from the battlefield to replenish mana. The Stronghold faction introduced in Tribes of the Eastowns this trope though. First, there's the "Slave Market" town building that lets you sell units for resources (ironic, given the Orcs' history as oppressed slaves). The Wyvern Upgrade, the Pao-kai, can consume dead creature stacks to heal and revive their own numbers. Their strongest unit, the Cyclops, can use Goblins (the weakest unit) as food and ammunition, making the poor saps literal cannon fodder. The Shaman upgrades, the Sky and Earth Daughters, are both able to sacrifice Goblins to replenish their own mana. In fact, this is the only way the Sky Daughter can use her "Chain Lightning" ability since she doesn't start battle with enough mana to use it. Her in-game creature description ends with this little gem: "Because of this, they are greatly feared by their opponents - and by Goblins". Not to mention that the Cyclop's description mentions that the Orcs bought the Cyclops' allegiance by offering them their favorite food: Goblins. Yeah, Goblins are pretty much the Stronghold's Buttmonkeys.
The manual for the RTS Earth 2150: The Moon Project contains several essays to bring the player up to date with the plot. One of the more memorable ones is a request for asylum from a disillusioned soldier formerly of the United Civilized States military forces, describing how the cyborg battalions of the last war disappeared only just prior to the invention of a portable AI module, large enough to store a human brain and a few electronics, that also has a very large warning stating the type of execution awaiting anyone who opens it. In another essay this is alluded to, as well as praising the soldier for anticipating the turn of events and defecting.
In Planescape: Torment, the Nameless One's immortality is fueled by other people's lives. To be more specific, whenever he gets killed, the force keeping him alive casts about the Planes, steals someone's life force, and forces it onto the Nameless One. Naturally, the people this happens to aren't terribly happy about it: they compose the monstrous shadows that stalk you through the game.
In the Neverwinter Nights 2 expansion Mask of the Betrayer the player is afflicted with a curse that makes him or her hunger for spirits, and able to choose to increase his or her power by eating said spirits. In addition to being obviously morally questionable, spirit-eating on a regular basis also has the downside of increasing the player's hunger to the point that he or she requires multiple spirits per day just to keep from dying.
Obsidian is REALLY fond of this one, it seems. In the second Knights of the Old Republic, the Jedi Masters explicitly state that the Exile is a "Wound in the Force," and not truly connected to it. Due to your connection to the Force being severed and your powers stripped, throughout your whole adventure, you siphon the Force energy from those you kill and your own party members (most of whom are Force-Sensitive and all of whom are in some sense bound to you) to stay alive, become stronger and use your Force powers.
In Quake IV, the main character eventually gains the ability to use a miracle healing fluid called Stroyent... which is created by using a bizarre cyborg monster to process liquefied human bodies. Indications in both this game and predecessor Quake II are that the humans are usually alive when they're liquefied — fortunately, the liquefaction process, although gruesome, does seem to kill them.
It also shows up in Enemy Territory Quake Wars as a dual health/ammo pickup for the Strogg team, and destroying a processing plant for it is the GDF objective for one stage, but its origins aren't directly addressed in that game.
Though it is part of the advertising campaign for Quake Wars. In spite of its Soylent origins, the advert that features it is rather hilarious.
You also see dismembered humans powering certain devices around the Strogg factories, as well as one powering the Makron, and they are also alive and at times trying to escape. Most of them appear to be heavily drugged, a state in which they're probably better off.
ResidentEvil: Survivor reveals that the process used to create Tyrants (one of the toughest enemies in the game) involves removing the pituitary glands from the brains of teenage boys after first producing a massive quantity of a chemical created by fear. The "improvement" Umbrella comes up with is to perform the surgery without anesthetic.
Shin Megami Tensei: Digital Devil Saga, in a rather disturbing version. Your characters (and, by extension, your enemies, who have the same power) get stronger by eating other people. Which they do. With frequency and sometimes gusto. Other demons, to be more exact. Killing humans actually gives you no Atma and you can't use Hunt skills on them either. It's definitely as per the above as far as the backstory is concerned, though. In the main franchise, there are several examples of farming of a substance needed to soothe demonic hunger, called variably Magatsuhi, Magnetite, or Red Pills, which is just as variably identified as a distilled, concentrated form of human souls, emotions or neurotransmitters. It's perfectly possible for a single human to generate enough to sustain a small team, but larger operations like the Nightmare System or Reverse Hills require massivePeople Farms.
In Star Control, the ships of the sinister Druuge can restore their energy meters faster by tossing members of their crew into the ship's furnace.
Their entire culture revolves around this. They consist of just one company, the Crimson Corporation, which owns everything. So any Druuge that transgresses is fired, which immediately leads to them being guilty of stealing Corporation resources (such as air), at which point they feed the furnaces. The creators of the game are quite proud of this little bit of nastiness.
In The Sims 2, a Cowplant's milk can grant the drinker an extra five days of life, at the price of one human life a pop. Sims can roll wants to "drink" their enemies.
Video Game Cruelty Potential if there has ever been any. If you want to be especially evil you can feed your entire neighbourhood to the Cowplant, making your own Sim immortal by eating the souls of children, so to speak.
In the doujin game Sora, Starbreaker has to tie herself to a satellite in order to attack the earth.
In Star Flight, it is revealed that the fuel used to travel in hyperspace is actually the long 'lost' ancients. Even more, the mysterious crystal planet that is the big threat of the series is actually a defense system constructed by the ancients to fight the mysterious and horrible monsters that are kidnapping their people and burning them alive to power their star ships.
Tales of Symphonia features Exspheres, a form of Magitek symbiote mass-produced by the villains that empower their wielders with superhuman abilities and can be used to power Magitek devices. They are eventually revealed to be powered by the soul of a living being that has been killed slowly and painfully in the process of activating the Exsphere for use. What's more, those belonging to a few of the main characters turn out to contain the lives of their loved ones, and two more had "different", experimental ones that were stealing their lives. The heroes must use them anyway, because the villains certainly won't stop doing it.
Xenogears has a variation on this; the murderous pseudo-undead monsters known as Wels are revealed to be the byproducts of Solaris' human experimentation projects. At first, this causes the PCs to wonder if it's actually right to kill them... but then, it's further revealed that the reason they're murderous is that the experiments leave them in constant, maddening agony which they lash out with violence to try to relieve, and death is the only true escape left to them.
Also in Xenogears, the meat made in Soylent in Solaris is made of Wels.
In fact, the entire Soylent System — a mechanism used to reabsorb mankind and Wels for their raw materials — is a reference to the actual Soylent Green movie.
In Xenosaga, the nerve cells of Realians (who are basically "Bio-Androids" or human beings specifically made for certain tasks) are eaten as a drug. Arguably this is Squickier then if they were used for a food source. As least sustenance is a need.
Cecily and Cathe.
Fable II features Reaver. First, his eternal youth and good looks were put in place by sacrificing the entire population of Oakvale, albeit by accident. Second, continuing to have those good looks comes at the price of tricking someone to give up their own youth and beauty.
Try almost every enemy in Half-Life 2. There's a reason the Big Bads are known as the Combine (as in harvest). Combine mooks? Normal people with most people-bits taken out and cyborg alien science put in. The Headcrab zombies? Turns out the 'zombies' underneath the Headcrabs aren't all the way dead (and their screaming is some of the most potent nightmare fuel in the game). This makes the Zombine (a Combine soldier zombified by a Headcrab) a double-whammy. The Striders? Same thing as the "human" soldiers, but with another alien race. The same goes for their Dropships and Gunships, by the way. And who's in charge of assembling these things? The Stalkers. Humans with their limbs cut off and their vital organs removed, but kept alive and utterly dependent on obeying their orders. Walking is a privilege they have to earn, as are eyes. Without effort on the viewer's part, they're no longer recognisable as human. Alyx puts it best. "I hope you don't remember who you were."
In Galactic Civilizations there is a chance that any particular planet that is being colonized will have something special on it that lets the player choose from three options: Good, Neutral, and Evil. Many of the evil options (and some of the neutral options) are of the Forsaken Child variety. For example, a life form on the planet links people together to create a psychic network that gives a huge improvement to science production on the planet, but the people must permanently enter the life form's pods (signified by a reduction in population). The options are: (Good) Cordon off the area and allow NO ONE to enter.(Neutral) Hook up only the infirm and the elderly. (Evil) Excellent! Hook up a random selection of the population.
Yuri's household in Red Alert 2:Yuri's Revenge would make even NOD shiver with unease. He got power from bio-generators (like in Matrix) that could be enhanced by placing additional humans in them. His primary harvesting facility was a Slave miner and the secondary one was a huge Grinder that processed humans into credits. He used cloning vats to churn out infantry and his super-weapon turned humans into bulky brute mutants. Oh, and all his army was mindcontrolled by him. What a jerk.
It's not surprising that his spiritual successor in Red Alert 3, Yuriko, runs on the same logic. However, she is the forsaken child. As Uprising reveals, her Psychic Powers alienated her from everyone in her village, and she was taken by the government at a young age and brainwashed into being a mindless killing machine. Even when she breaks free after the war, she's forced to kill her own sister, and her revenge leaves her feeling empty inside. That's not even mentioning the thousands of expendable clones, all of whom apparently felt the same things she did.
World of Warcraft's Scourge qualifies for horrible often enough, but the creation known as Thaddius fits this trope specifically, being made up of the souls and bodies of women and children slaughtered in conquering Lordaeron.
The Lich King's sword "Frostmourne" can absorb the souls of those it slays to power up, or to turn the slain into Scourge, controlled by the Lich King.
Its sister weapon, the player-obtainable axe "Shadowmourne" must absorb the souls of 1000 entities from Icecrown Citadel as part of its manufacturing process before it gains its full power. The visual effect of the buff it grants the wielder is a vortex of the absorbed souls swirling around the player.
One of the older and more notorious World of Warcraft examples was the "Chained Essence of Eranikus" item which created a poison cloud around the player, the downside? The item is powered by the tortured soul of a dragon who begs for mercy (and occasionally threatens) everytime the object is used.
While by no means a required facet of gameplay, The Elder Scrolls series allows such behaviour. In Morrowind, soul gems can be used to eternally trap the souls of defeated monsters, and the resulting soul can then be used to fuel a magical weapon. However, Oblivion lets you take the same concept that little bit further, with the use of "black soul gems", a variant favoured by Necromancers that allows the trapping and fusing of human souls. In fact, human souls create the most powerful enchantments in the game. Not that every magical item could be eternaly fueled by an innocent animal's soul such as elks, foxes or even rabbits is any comfort.
The Shivering Isles takes this a step further with Dawnfang/Duskfang. To start with, it's a magical weapon and so must be recharged with soul gems. What's worse, it changes damage type with the day/night cycle (fire by day, frost by night), and each time it switches it can become (for the next 12 hours) a stronger version of itself... if the other form was "fed" 12 souls. So in order to keep the blade perpetually in its Superior state, one has to let it claim 24 souls EVERY DAY * and* make sure the enchantment itself is charged with souls. Add that to the rather disconcerting toothy maw of the blade, and one begins to wonder what sane hero would willingly carry this on her person.
In Skyrim, the Ebony Blade has turned into this as well. In the previous games, it was merely a particularly powerful Ebony Dai-Katana with some nice buffs. In Skyrim, it has a Life-Steal power that can be enhanced... by using it to kill people who love you. (In in-game terms, any NPC you've completed enough quests for to make them 'like' you.) In its base form, it's marginally useful. Fully-boosted - which requires you to murder 10 people who consider you a friend at the very least - it provides a powerful life-steal with infinite charges, making you extremely hard to kill in a melee.
The Dwemer who are a dwarf/gnome combo even though in game they're elves did SOMETHING to the Snow Elves to turn them into Falmer. Snow Elves as sentient beings would require a very rare black soul gem to put their souls into soul gems but as Falmer much cheaper soul gems work. A lot of Dwemer technology relies on soul gems.
The Daedric equipment is this by default: each piece of Daedric armor and weapons is Ebony with a Daedra soul infused into it at creation. In Skyrim, the first installment that actually lets you craft Daedric equipment, this manifests in having to spend a Daedra Heart (an alchemical ingredient gained from killing certain Daedra) on each crafted piece.
Averted in Metroid: Fusion (which takes place after the Prime trilogy). Samus survives her initial encounter with the X Parasite due to a vaccine derived from a baby Metroid; however, all study by the scientists was carried out either humanely or posthumously after Mother Brain killed it in Super Metroid.
All of Pathologic's healers' techniques involve this to some extent.
In the third Thief game (Deadly Shadows), the Old Gray Lady has killed an orphan to use her shape as a disguise. Garrett restores the orphan's soul to her body, which destroys the disguise and advances the plot.
Mass Effect 2 combines this with Player Punch in the final mission. In order to reproduce, the Reapers have to capture alive billions of sentient beings, liquefy them (which you potentially see done to most of your crew first hand), and inject the genetic material into the mechanical portion of the Reaper. This makes ONE Reaper. There is evidence to suggest that a Reaper cycle happened thirty-seven million years ago; assuming that this was the first cycle, and that's a big assumption, there are over seven hundred Reapers.
As well as the Overlord DLC, where David, an autistic man, was hooked up to a VI so that he could communicate with the geth, perhaps control them. His physical body is suspended, naked, in the centre of the machine, wires jammed beneath his skin, into his mouth, and his eyelids pinned back. Arguably even more horrifying is the mental effect, however - the over-stimulation is obviously near-unbearable even before David enters the machine. When he does, he begins screaming in agony and terror... Those horrible high-pitch distorted screams you heard all mission? That was David desperately pleading with you: "Quiet! Make it stop!!!"
BioWare also had this trope runnning in Jade Empire. The Emperor has ordered Death's Hand and the Lotus Assassins to hire slavers to raid "insignificant" villages. These villagers are brought to the Lotus Assassin base and killed by some kind of alchemical acid, leaving behind a Soul Jar that's used to power the terracotta army they're building.
That's just an extension of the worst act. The Water Dragon's mutilated body is kept as a trophy in the Palace. Its power is siphoned by the Emperor to grant him strength and vitality. The Dragon's blood is water, and so its body was carved open, allowing a flood of water to pour out of the Palace and into the Empire's rivers and lakes.
Dragon Age: Origins has the golems, who were created out of people. Some of them volunteered to have molten rock poured over them and give up their free will. When they began running short on volunteers (and when the dwarf who invented the technology suffered an attack of conscience), the king started conscripting his subjects and sent the inventor through the process himself.
Also, a defeated blood mage will offer to magically increase your strength and endurance in return for his life, all it takes is sacrificing the lives of all the elf slaves you came to free, one of whom, if your character is a City Elf, is your father.
The trope is the force that drives the plot of all the F.E.A.R games. Defense contractor Armacham Technology Corporation started a project to train psychic commanders to lead mass produced clone soldiers. To get adequate, controllable psychics (the goal was for them to eventually be reliably producible as products), the head researcher believed the commander embryos can't just come from a psychic's DNA but also need to gestate inside a psychic... so... they take Alma, a disturbed, psychic 8 year old girl, put her in an induced coma, lock her away in a machine in "The Vault" underground for years until she's ready for pregnancy, and pump two children out of her, putting her back into a coma each time. Did we mention that the father of those children is Alma's father? Despite being in a coma she's eventually able to psychically reach out to one of the young commanders and get him to kill some of the researchers in revenge. This convinces the researchers to shut down the power to the facility holding Alma, so naturally she dies a few days later. Turns out when you forsake a psychic child that badly, being dead doesn't stop her from taking revenge... Alma reaches out to the psychic commander again, jump starting the plot.
The Soul Reaver in the Legacy of Kain series drains the souls of enemies in order to power itself up. However, the whole reason it can do this in the first place is that a maddened, ravenous spirit is trapped inside the blade... a spirit that just happens to belong to the protagonist of two of the games.
The Angelic Rifle in Baroque fires bullets that contain the Littles, which are living incarnations of pain extracted from the Absolute God and look like winged, misshapen human babies.
The Void Walker skill Breath Of The Dead Child from Nexus War does Exactly What It Says on the Tin. in-game it's powered by magic points, but according to the fluff, the demon infiltrates the paediatric ward of hospitals, harvests the dying breaths of children, and unleashes them later, causing the children's tormented souls to bite and gnash at his foes. Hope you weren't planning to sleep tonight.
In Super Robot Wars, Jurgen's ODE System which was used to command the Bartolls which required living humans hooked up to cores. The Mironga, a variant merely has the pilot using the system linking them directly while maintaining some will of their own. The ATX and SRX team were shocked to learned about this, the fact that Lamia was used as the main nexus of the core prevented further victims from being used for the ODE System as the newer ones were totally unmanned
Nearly everything in BlazBlue is Powered by a Forsaken Child. The Magitek that the world is so heavily dependent on for its survival relies on seithr, The Corruption created by the Black Beast that made it necessary in the first place, and the Beast itself was an attempt to gather the souls needed to create a magical superweapon that went horribly wrong. The Nox Nyctores that several characters use in battle were also created by sacrificing thousands of human lives to create each one.
On the subject of Nox Nyctores, nasty bastard though he may be, Relius states that it is possible to use fewer souls to make a Nox Nyctores, but the reduction is highly dependent on the quality of the souls used. A focused soul is higher-quality than a scattered soul, and a multilateral soul higher quality than a unilateral one. By that logic, a focused soul, pointing in multiple directions, is of the highest quality possible, and could very well be used to make a Nox or "detonator" on its own. That should explain a lot more about his "obsession" with Makoto...
In Fatal Frame, the reward for the eight-year-old who wins a game of demon tag is to spend ten years locked in total isolation before being torn apart by ropes, all to keep the Hell Gate closed. The loser doesn't fare much better, having stakes stabbed into her eyes and becoming "it" for the next game of demon tag.
In Chaos Legion, the legions Sieg uses are made by sacrificing wandering human souls, a fact foreshadowed by a line in its opening cinematic.
The Garland device in Hellsinker is powered by four dead children buried beneath it. To get the best ending, you must face Garland, then defeat the spirits of the children, who have taken a great interest in a cat and insist on bringing it into battle.
Alice: Madness Returns has the Dollmaker power the infernal train with the bodies of insane children, which reaches horror levels when you realise the very deliberate pedophilia subtext in that level.
In Deus Ex: Human Revolution, the Hyron Project is a immense quantum computer/security system powered by three women trapped in life support pods, who constantly beg to be allowed to sleep. To increase the creepy factor, it acts like a normal computer system, but ends its official announcements with disturbing messages. These women don't survive for very long and a DLC reveals there is a secret base which kidnaps women, "processes" them and ships them to the Hyron Project. Their experiences throughout this are suffering defined.
And those system generated passwords? Hyron employees keep complaining in internal email how creepy they sound...
In the original Suikoden, the Rune that Governs Life and Death works like this - it's pretty powerful even at the worst of times, but it grows stronger by devouring the souls of people loved by the wielder. Friends, family, 's all good. He doesn't have to kill them directly, but nor does he get to choose - the Rune itself seems to employ some form of probability manipulation to bring about the death of the loved ones so it can grow stronger. On the bright side, it's literally the most fearsomely powerful Rune that has ever appeared in any of the games, so hey, at least you got something OUT of all those tragically dead family-members and close, long-time friends...
In Baten Kaitos Origins, Baelheit's machina is powered by afterlings, gigantic creatures that are the result of a failed experiment to implant pieces of a dead god into humans. It's never made clear if the victims are still aware.
In Alundra, it's no coincidence that you gain new items whenever someone dies: Jess is able to craft new weapons thanks to the spirits of deceased villagers who wants to help Alundra.
In Xenoblade, the Mechon are draining the ether (basically the life-blood) from the slumbering god/titan Bionis and converting it into a universal poison for all life-forms that were born from the Bionis. It turns out they were doing this to stop the Bionis from absorbing said life-forms and using them to refill its life energy, making an even straighter example.
In Radiant Historia, the world relies on Sacrifices willingly giving up their souls to keep it from becoming a lifeless desert. The entire plot is kicked off by one intended Sacrifice's attempt to Screw Destiny not only for his own sake but for the sake of the next chosen Sacrifice the player character.
In the section of Ecco The Dolphin: Defender of the Future where dolphins turn into jerkasses and take over the world, the three highest members of the ruling class have sequestered themselves off in giant water bubbles high in the sky. The only way up to them is to turn on the Hanging Waters tube system. The only thing that can power the Hanging Waters is the life force of enslaved whales.
The Kushan mothership in both Homeworld games is so large and complicated that no conventional computer system or crew can manage it. As a result, a system is created that involves permanently surgically implanting a living person into a Wetware CPU so that the various subsystems can be managed directly. The system's creator, Karan S'jet, volunteers herself, partly because she understands it best, and partly because she wouldn't trust anyone else with it. At the end of the game, Karan is disconnected from the Mothership. In Homeworld 2, taking place several decades later, she connects herself to the new and improved mothership Pride of Hiigara to serve in the same capacity.
Pokémon X and Y features the "Ultimate Weapon" created by Kalos's king, AZ, three thousand years ago. It sucks life of dozens, maybe hundreds, of Pokémon and can be used as either a device to give eternal life or basically a nuke. AZ used it in the past to revive his beloved Floette, and in the present Team Flare plans on using it to wipe out all people for the sake of the planet.
In Dark Souls and Dark Souls II, this is the dark secret of the Age of Fire. The First Flame that sustains the Age of Fire (and more importantly keeps the Dark Soul from becoming an Abyss that consumes everything) must be rekindled every now and then with a sacrifice. Not just anyone will do either, the sacrifice must have a very powerful soul. In the first game's backstory, God Emperor Gwyn sacrificed himself to Link the Fire, and one of the endings has the player character repeating the sacrifice having proved themselves to be worthy by passing all of the trials needed to reach the Kiln. In the sequel, the Undead Hero does the same thing in the end.
In Ad Venture Capitalist, restarting the game earns angel investors that increase your profits. Some of the upgrades require sacrificing angels, although you must careful consider the cost of losing their multiplier vs the benefit of the upgrade. (At first anyway. Eventually you have so many angels it's a non-issue.)
In Labyrinths of the World: Shattered Soul the villain uses your sister's soul to power an invention allowing him to travel to different realities.
8-Bit Theater features a rather humorous example: Black Mage's Hadoken is powered by love. No, just sit there and I'll rephrase it. Every time BM launches a Hadoken, he siphons love from the Universe and twists it to highly destructive ends, making it create an explosion that consumes love (the divorce rate rises, for example). Not that he cares, but Red Mage seems to.
The Hadoken was also received by BM after sacrificing several orphans.
Of course, he would have sacrificed the orphans anyway. A hobby's a hobby.
Oh no, it would've been horrible if he had done it for no reason. That being his defense when White Mage loses all respect for him after hearing the above.
Black Mage: It takes the happiness of others and turns it into pain and explosions. It's win-win.
In Sluggy Freelance, Torg's magical sword Chaz is powered by the blood of the innocent. He's only able to make much use of its full power when in a Sugar Bowl dimension being invaded by sadistic demons, so that there's plenty of such blood being spilled by others.
In Looking for Group, Cale has to kill an innocent child to save the city of Kethenecia.
except it is not a real child, but the Archmage in disguise
One of the themes for that chapter was that "Innocence is the cost of justice." This leads us to believe that the aforementioned child must be killed to save the city of Kethenecia (the city of justice). After it is revealed that the child is the Archmage, he states that the innocence is not some nameless child, but the innocence of Calenon.
In Homestuck, Her Imperious Condescension (the Troll Empress and the ancestor of Feferi) has a flagship that runs upon the immense psychic powers of The Ψiioniic, the Ancestor of Sollux—causing him excruciating agony. Also, trolls lower on the hemospectrum (like the Ψiioniic) live comparatively short lives, so the long-lived Condesce extended his lifespan with her magic. He's been her Helmsman for thousands of years until the Vast Glub happened, rendering the Condesce the only remaining troll in the galaxy (as tyrianbloods are immune to Gl'bgolyb's psychic scream and Feferi was in SGRUB's game world).
Vriska at one point theorizes that Sburbmust be played only by adolescents.
While we're on the subject: Trolls each get a lusus (a sort of guardian) at "birth" that takes care of them until they reach adulthood. Eridan kills the lusi of other trolls and gives the corpses to Feferi for Feferi's lusus Gl'bgolyb to eat, making Gl'bgolyb powered by causing children to be forsaken. But it's for a good cause, really: if Gl'bgolyb doesn't eat, she'll start complaining, and then every troll in the world starts dying. Meanwhile, Vriska has a use for all those forsaken, guardianless children: she feeds them to her lusus, a giant spider. By the time the trolls reach the age corresponding to about 13 in human terms, they've been doing this for years.
In Spacetrawler, the construction of the eponymous spacetrawlers is implied to involve horrific abuse of Eebs, and when the details are eventually revealed, they're every bit as bad as implied: an Eeb is trained to telekinetically gather space debris—by injecting them with a drug that causes debilitating pain if they ever stop gathering said debris. Then the Eeb's body is dissolved, while still conscious, and their Brain in a Jar is placed in the spacetrawler.
Narbonic includes a time machine with the drawback that its use requires all the energy of the universe. Dave Davenport figures out how to use the time machine by having it comsume all the energy of a parallel universe. He assumes they just don't want to live as much as the people in his universe do.
One of defences Gunnerkrigg Court got is a bound ghost. Who is extremely unhappy about the situation for several very understandable reasons. The records were cleaned and those who meet this guardian in person are unlikely to survive, thus most of the current generation are blissfully unaware of this, except a team secretly searching for a way to remove this old shame.
In the short miniseries, Freako Asylum, the two protagonists go to "The Twisted Machine Of Science" to answer their questions on how to handle the situation. In its center is an infant hooked up to the machine. Unusually for this trope, the kid looks positively jolly and is dancing around in his/her seat.
Linkara'smagic gun is powered by the soul of a little girl sacrificed by her parents to their evil god. That's where it gets... weird. To be clear, he only found out when the viewers did, and was as horrified as you'd expect. He almost shot himself with the gun, but the girl's soul talked him out of it.
This quote, taken from Llamas with Hats: "I should probably mention I filled our luggage with orphan meat." "Wh...what?" "Well, I'm building a meat dragon, and not just ANY meat will do!"
It turns out in the Whateley Universe that uber-powerful mage Fey's best spells are powered by energy from ley lines, and that in some of the battles already fought in earlier stories, she ended up destroying neighboring ecosystems.
A more classic example is the fate the Bell Witch intended for her daughter: to turn her into a god-like being, then enslave her to serve as the source of her own power. Fortunately, not only does Nacht turn on her mother, as a result she gets the one thing she always dreamed of, proof that Marzena isn't her real mother, breaking the hold she had over her.
One SCP Foundation short story involved "button day"; entire families voluntarily submit to/are brainwashed into suicide by melting to combat overpopulation.
Actually, let's just say that a lot of the SCP Foundation's activities are this and save ourselves some time.
In one episode of Adventure Time, Finn is kidnapped by gnomes to power their device to flip over the Earth's crust.
In an episode of The Venture Bros., Doctor Venture's family is trapped one by one inside his latest invention, a simulator known as the "joy can" that grants the user's fondest desires. One of its vital components was the heart of an orphan. Doctor Orpheus's disgusted response became the new Trope Namer.
Starscream's clone technology of Transformers Animated involves the use of protoforms, which can be described as fetal or pre-natal Cybertronians.
In Argai: The Prophecy, QueenDark gains and maintains her immortality by stealing the youth of several maiden throughout time and keeping them in eternal slumber.
Galaxy Rangers has the Psychocrypt. Literally sucks out Life Energy to create Slaverlords through which the Queen can see and hear. In this fashion, she can keep direct control over her armies and her crumbling EmpireThe Queen of the Crowns already hunted the Gherkin race to near-extinction in her thirst to create Slaverlords. Then, she discovers humans, who are ''ideal'' specimens to create Slaverlords. A good deal of the Rangers' job is to keep the Queen from obtaining more humans for the Crypt. The process, as seen in "New Frontier" & "Psychocrypt" is also horrendously painful.
A more mundane and light-hearted example found in The Simpsons: Homer is forced to turn a gigantic wheel, with a guy with a whip egging him on...in order to operate a rotating display in the break room.
Homer: Ow! D'oh! After lunch, can I whip you?
Slave-driver: (cheerfully) Nope.
Homer: Oh, no fair. Ow!
(pan to the plant lunch hall, where Lenny and Carl observe the rotating dessert table)
Lenny: Hmm. Wonder what makes it turn.
Carl: Who cares?
Subverted in Mighty Orbots where Ohno, a robot shaped like a little girl, is the necessary ignition function for the Combining Mecha to operate. However, she doesn't mind at all since she's designed for it and once that function is complete, she disengages to become the Commander's copilot.
An older version in the The Fairly Oddparents: Fairy World is powered by belief in fairies. It would be Clap Your Hands If You Believe, if not for one little issue: the only belief that apparently matters is Crocker's. A man who does not remember having fairies, but knows they exist and is completely obsessed with them. Fairy World is thus powered by the spazzes of a forsaken former godkid.
To prevent all of Fairy World disintegrating should Croker die (having magically guaranteed that he'll never get over his issues), several more Croker-alikes are given his obsession.
A bit of Fridge Horror for this one but watch the Cap'n Crunch Commercials: To make the transition from live to cartoon via Crunitize they are turned into the cereal, so does that mean the cereal is made of little children who couldn't survive Crunitizeing?
One urban legend featured on the Darwin Awards told of an accidental case of this: an employee at a power plant looking to lose weight tried to use their coal runner as a treadmill, but tripped and was converted into power for hundreds of homes.