->'''Xamot:''' (''grunts in pain'')
->'''Alpine:''' Hey, I never laid a glove on you!
->'''Xamot:''' [[TwinTelepathy I feel... what my brother feels...]]
->'''Alpine:''' Terrific! Pass ''this'' on! (''punch'')
-->-- ''WesternAnimation/GIJoeARealAmericanHero''

Two people are linked together, or a person is linked to an object, such that whatever happens to one also happens to the other. Killing or harming one of them will lead to the death or equivalent harm of both. You wouldn't think this would be desirable, but it works the other way too; see EmpathicWeapon.

If enemies are linked together, and are therefore forced to protect or aid each other to ensure their own safety, this becomes a form of ChainedHeat.

Identical twins on TV often experience this, as with ''The Corsican Brothers'' of literature. It's also common with the EnemyWithout.

Frequently goes hand-in-hand with a PsychicLink, because YourMindMakesItReal, and sometimes with MindLinkMates. Compare MySignificanceSenseIsTingling. Often [[PowerPerversionPotential exploited]] for [[DirtyMindReading very]] [[FetishFuel interesting]] [[RuleThirtyFour effect]]. See also SharedLifeMeter, a related video game trope.

If the link can ensure the death of a participant but doesn't otherwise transmit pain or other feelings, then it isn't a Synchronization but a case of CantLiveWithoutYou.

----
!!Examples:

[[foldercontrol]]

[[folder:Anime & Manga]]
* ''Anime/NeonGenesisEvangelion'': The mecha pilots use neural links to control their Eva units. A meter shows the "synchronization ratio" which depends on several factors including plug depth (increases synch but puts the pilot under more strain as well as risking mental contamination by the Eva) and the pilot's psychological state (being depressed lowers the synch ratio). Low synchronization means you can't pilot the mech at all (it won't even move under 20%), and higher synchronization ratios give the pilot better and better control. It's made clear that higher synchronization ratios are dangerous in various ways, but it's not completely explained. Examples:
** On one occasion a pilot was saved by cutting the link a split second before the mecha was beheaded.
** When his synchronization ratio exceeded 400%, [[spoiler:Shinji dissolved into his mech and had to be reconstituted. It is said that the same happened to his mother but she didn't come back.]]
** Similarly, after [[spoiler:descending to a dangerous plug depth in order to save Rei]] in ''[[RebuildOfEvangelion Evangelion 2.22]]'', [[spoiler:Shinji became trapped in the entry plug for ''[[TimeSkip fourteen years]]'', finally being recovered from Unit 01 in the beginning of ''Evangelion 3.33'']].
** In ''End of Evangelion'', Asuka's ratio reaches 300% and [[YourMindMakesItReal the injuries to Unit 02 are reflected on her body]]. [[spoiler:Seeing that she ran out of power just as she was [[EyeScream speared in the head]] and that her opponents were, for all intents and purposes, [[ImAHumanitarian cannibalistic]] [[AxCrazy harpies]], it isn't necessary to elaborate the result.]]
** It's said that the Eva units' synch rate depends on the pilot's need to "run to mommy". Which is why the units tend to go BERSERK and start acting on their own in moments of extreme turmoil. This is also why, in the original series, Asuka's synch rating actually goes down as she comes to grips with her mommy issues, to the point where she can't even pilot anymore.
* A similar system is used on the [[HumongousMecha Endlaves]] in ''Anime/GuiltyCrown'': pilots are synchronised to their machines via remote interface, though they feel everything the machine does, and Ayase seems to show physical manifestations of damage to her Endlave on her actual body. How a machine is meant to feel pain (and indeed why you'd build in a system which incapacitates your pilots with extreme pain if their machines are destroyed when hot-swapping pilots between machines can be done instantly) is beyond explanation.
* ''Franchise/{{Digimon}}''
** Likewise Tamers and their partners in ''Anime/DigimonTamers'', once they reached a certain level.
** In ''Anime/DigimonAdventure02'', Jogress Evolution (DNA Digivolution in the dub) was achieved (three times) when two of the human characters synched emotionally with each other, merging two Adult/Champion Digimon into a single Perfect/Ultimate. At least one of the three examples came along with a synchronized ''heartbeat'' from the two characters in question.
* ''Manga/FushigiYuugi'' features twin brothers Amiboshi and Suboshi, who felt everything that happened to the other, a la ''The Corsican Brothers''. Also, for a while, Yui was synchronized to Miaka, so that (for instance) when the latter was drowning, the former couldn't breathe.
* At one point in ''Anime/VisionOfEscaflowne'', Van became synchronized to Escaflowne. While this allowed him to win the battle in that episode, it also resulted in him taking serious injuries, and the only way to treat them was to get Escaflowne fixed (with poor Van screaming and [[HeroicBSOD BSODing]] in pain as it's done, since fixing Escaflowne is almost like fixing any machine, only more complex and taking the mental/physical link in consideration. And considering that Escaflowne [[PaintItBlack turned black]] when it happened, synchronization could also count as a SuperpoweredEvilSide.
* ''Anime/YuGiOh''
** In many battles, the duelists seem to be physically weakened by the carnage going on in the card game. In many cases there is some sort of supernatural explanation for this, but it sometimes happens even when no supernatural forces are at play. There is some sort of weak implication that the realism of the holographic systems used causes a stress response in dedicated players -- in one early duel, Yugi's grandfather Sugoroku actually has a heart attack when he loses. Kaiba certainly seems to believe that using his own advanced holographic systems gives him an edge, as his opponents are overwhelmed by the realism of the simulation.
** Yami and Yuugi could arguably be this as well, what with the whole [[SharingABody two-souls-sharing-one-body]] business; they're usually in tune with each other's emotions, thoughts and, shown at least once, feel each other's pain. Not to mention that it has been implied that if one of them is killed, the other will die as well.
* The Emilys in ''Anime/SoukouNoStrain'' shared a psychic connection first seen when Sara encounters the doll and names it, and the girl takes the name as her own. [[spoiler:The Emily race initially mounted against the Union because they felt their compatriots' pain at being dissected.]]
* ''Anime/RahXephon'':
** This is also implied (but not confirmed outright) to be the case -- in one fight, the [=RahXephon=] is impaled through the shoulder, and Ayato is seen clutching his own shoulder afterwards.
** It's more clearly the case for the people trapped into piloting the enemy Dolems. Ayato himself doesn't quite get this through his head until it's too late, though: [[spoiler: he has already indirectly ''beaten Hiroko to death'' by defeating the Dolem she's linked to.]]
* Mai and the demons in ''VisualNovel/{{Kanon}}''.
* ''Manga/JoJosBizarreAdventure''
** The Stands are effectively astral projections, and damaging them results in corresponding damage to its user. Additionally, in Part 3 a Stand user named Steely Dan had the power to inflict a "Corsican Brothers"-type bond on another person (for example, getting tapped in the leg with a stick led to his victim almost breaking his and having his back scratched caused the sensation of being flayed alive). He used this on Jotaro's grandfather and threatened to kill him if Jotaro didn't play along. He then proceeds to abuse him until the Stand is removed, upon which Jotaro (having written down all the abuse suffered against his person) beats the crap out of him with his own Stand. ''For three whole pages''.
** It is only because of this synchronization that Jotaro is able to defeat BigBad Dio Brando; [[spoiler: during their last battle, Jotaro strikes Dio's Stand in a place where Dio himself had been injured, and as a result, Dio's body practically shatters.]]
** In Part 6, Stone Ocean, Xander [=McQueen=] has the Stand "Highway to Hell" which synchronizes him to his victim whenever he attempts to kill himself. This is coupled with zero control over his own suicidal tendencies.
* ''Anime/{{Mai-Otome}}''
** An Otome's Master feels everything his or her Otome does. This was done because in addition to being a prettified bodyguard, an Otome is a WeaponOfMassDestruction. A Master whose life is on the line as well is theoretically less likely to engage in war. Likewise, a Master/Slave Unit in the same series.
** The Slaves that members of Schwarz use follow this principle. If one is damaged, the user is injured, and if one is destroyed, the user dies. The reverse is also true, as a sniper kills a Slave user, and causes the Slave to disappear.
* ''Manga/MagicKnightRayearth''
** The Knights are synchronized with the [[HumongousMecha Rune]] [[MechanicalLifeforms Gods]] they've [[BondCreatures established a contract with]]. If the Rune God they're riding is injured, it will wound the Knight herself -- to the point that breaking the Rune God's weapon will destroy the Knight's own Escudo sword. This synchronization is particularly evident in the AlternateContinuity {{OAV}}, where Alcyone's hand was torn apart (and remained a bloody mess afterwards) when Hikaru punched through her Rune God's claws.
** In the trial for escudo, while Hikaru and Umi face copies of their loved ones (Hikaru's puppy, Umi's parents), Fuu fights a fake version of herself, and each gets the other's wounds.
* The whole plot of ''Manga/{{Loveless}}'' revolved around the empathic connection between "Fighters" and "Sacrifices", in which the first are capable of commanding spells while the second suffer the effects of attacks in combat. The connection between both parties is vital to ensure victory and survival.
* Subverted in a rather cruel fashion in ''Anime/MaiHime'':
** [[spoiler:The [=HiME=] Childs are powered by the feelings their user has for another (their "Most Important Person"). When the Child dies, so too does the person (though not vice versa, apparently). When this comes into play in the anime (as it happens to pretty much every [=HiME=] by the end), the [=HiME=], whilst surviving, enters a HeroicBSOD (the first one even goes catatonic).]] There's also a sticky battle [[spoiler: between two [=HiMEs=] who share their 'Most Important Person' -- it's the same guy for both of them. As a result, whoever wins kills their Important Person... and in the end, the guy ends up dying. And he actually ''did'' tell the girl he actually liked to shoot the other's Child down, so she wouldn't die/BSOD because of him.]]
** One later battle [[spoiler:between two [=HiMEs=] who each consider the other their most important person ends with both of them dying when their Childs are destroyed. It's more exactly a MurderSuicide - one of the [=HiMEs=] deliberately had her Child shoot itself ''and'' the other dead so [[TogetherInDeath they would go down together]], even cradling the other girl in her arms as they die.]].
* ''Anime/GunXSword'':
** Van, who [[spoiler:was surgically reconstructed so that]] his life is synched to Dann of Thursday, his Armor. He grows ill if he spends too long without riding it, and if it's seriously damaged he suffers as well. If it's destroyed, he dies. Oddly enough, although no surgery is in his backstory, Ray Lundgren has a similar occurrence -- [[spoiler:when Carossa hurls a giant shuriken into Volcade's eye, Ray's vision goes permanently blurry]].
** [[spoiler:Ray's problem was likely caused by the electric shocks he received when Volkein took damage, or from hitting the back of his head when knocked backwards (which can cause blindness and eye damage).]]
* In ''Manga/FullmetalAlchemist'', when Ed gets severely injured, Al blanks out. This is because [[spoiler: Ed and Al are linked, and that Al's body is actually feeding off Ed's--which is part of the reason why he's so short]].
* In ''Manga/CorpsePrincess'', the death of a contracted monk usually leads to the death of his Shikabane Hime. If she goes on living, she is considered just another Shikabane and must be executed.
* In ''VisualNovel/HigurashiNoNakuKoroNi'', Rika is implied to share this sort of connection with Hanyuu, though it is played for laughs rather than drama, with Rika threatening to eat spicy food whenever Hanyuu fails her. One would assume that either the connection is one-way, or Rika has a much higher pain threshold than Hanyuu [[spoiler:due to all those horrific deaths]].
* In ''Manga/{{Bleach}}'', Captain Komamura's bankai is a giant warrior that mirrors his movements, and any damage inflicted on the bankai will in turn be inflicted on Komamura's body. Since no one else's bankai has this problem, it makes his power in particular a double-edged sword. His typical strategy is to finish his opponent with one blow. The link does, however, come with the advantage of the bankai being able to heal if severely damaged, something no other bankai is capable of.
* Basil Hawkins, a minor character in ''Manga/OnePiece'', makes use of [[HollywoodVoodoo voodoo dolls]] that somehow transfer any damage done to him to whatever unlucky sap he managed to make a voodoo doll of.
* Yuka and Mika, twin girls in ''Hot Tails'', share not only each other's pain, but also pleasure. Since ''Hot Tails'' is a {{Hentai}} manga, you can guess how this is applied. To be a tad more specific, Yuka goes out on a date, and Mika, bored and a bit irritated, [[ADateWithRosiePalms entertains herself]]. This makes Yuka's trip to the park with her boyfriend a bit more interesting.
* ''Manga/{{Naruto}}''
** Hidan can turn himself into a living voodoo doll. Any damage he suffers would then happen to his victim. Since he is immortal, he can easily kill someone with this ability. It is, in fact, his favorite way to kill people. His tactics almost all revolve around setting up this technique and then "killing" himself. [[spoiler:A fact that Shikamaru uses against him.]]
** Yamanaka Ino could do something similar with her clan's Valentine jutsu, which allows a shinobi to invade the mind of another, at the expense of leaving the practitioner's body comatose and suffering damage equal to the possessed body. Her teammate Nara Shikamaru's family has a similar jutsu; one stretches one's shadow out to lock on an opponent, making the practitioner and the victim move identically. The latter has shown itself to be less impractical, and has been used in combat a few times over the series. It helps that Shikamaru is a TeenGenius and very respectable strategist. They later show advanced versions of this technique, which don't have this disadvantage, but are harder to perform.
** A limited variant of this applies to Shadow Clones. If said clone is gathering nature energy and overloads, thus [[TakenForGranite turning into stone]], the creator will suffer the same fate.
** In a ''Manga/{{Naruto}}'' filler arc, Naruto faces [[spoiler:what seems to be]] [[TheDragon Kabuto]] in one of [[BigBad Orochimaru]]'s hideouts. Kabuto uses a DangerousForbiddenTechnique of which connects the hearts of the user and the victim through chakra strings. He then proceeds to remove his own still-beating heart from his chest and squeeze it, causing Naruto to take damage as well.
* In ''Manga/{{Kurokami}}'', a Tera guardian and a human can form a pact to sync up their "Tera", granting the guardian great strength, though this can be physically tiring to the human partner.
* Played for laughs in ''Anime/SonicTheHedgehogTheMovie'', in which Sonic and Hyper Metal Sonic achieve synchronization while fighting each other. Cue a scene where Sonic suddenly grabs his head in pain while grinning mischievously. Hyper Metal Sonic just got a peek up Sara's skirt and got kicked in the head for it.
* In ''Anime/EurekaSeven'', Coralians are linked to the Scab Coral. If the Scab is being attacked, all Coralians will feel the pain at the same time, hinting that Eureka will die if the Scab Coral is dead. It becomes an important reason for the protagonists to stop Dewey's plan to annihilate Scab Coral. This synchronization caused Renton [[spoiler:to lose his beloved Eureka in the manga ending]], while in the movie ending, [[spoiler:Eureka managed to "work around" this fate (The explanation of how it happened is up to debate, but you can't deny that PowerOfLove plays a huge part in this happening).]]
* In ''Anime/RoninWarriors'' (''Yoroiden Samurai Troopers''), the first Dynasty Warrior that Ryo fights causes this effect between himself and Mia (Nasuti) and Yulie (Jun), so if he gets injured, they suffer all of the pain. Ryo eventually defeats him by using his armor's power. (Though how this didn't kill them is not explained.)
* In TheAnimeOfTheGame for ''VideoGame/{{Persona4}}'', [[AstralProjection Personas]] act more like [[Manga/JoJosBizarreAdventure Stands]] than in the games. The protagonists do all their fighting through their Personas, and feel any harm that afflicts said Personas.
* Meldy from ''Manga/FairyTail'' links Gray and Juvia together so she only needs to kill one to kill the other. Despite being burdened by experiencing each other's injuries, the two are too tough for Meldy to defeat, so she resorts to linking ''herself'' to them, [[TakingYouWithMe then attempting suicide]]. [[spoiler: Meldy is stopped because the link allows the targets to feel each other's emotions, and [[ThePowerOfLove Juvia's feelings for Gray overwhelm her]].]]
[[/folder]]

[[folder:Comic Books]]
* Old Lace, the psychic velociraptor, in ''ComicBook/{{Runaways}}'', with her owner Gertrude [[spoiler:and later Chase]].
* The 1970's DCComics character ''Kobra'' had this problem; he and his twin brother suffered the injuries the other one got, so his brother was an enemy he could not kill. Kobra eventually got around this with some AppliedPhlebotinum to break the psychic link.
* ''Franchise/{{Transformers}}''
** In ''ComicBook/TransformersLastStandOfTheWreckers'', Topspin and Twin Twist have "vicarious preception" (basically a fancy name for this trope). [[spoiler:Eventually, Twin Twist ends up being tortured by Decepticons, and the other Wreckers are at a computer where the password-bypass system is for someone to sacrifice themselves. Topspin decides, knowing that his brother is in serious pain anyway, to [[HeroicSacrifice offer himself to the computer]].]]
** In the original Marvel Comics [[ComicBook/TheTransformers Transformers]] series, Megatron and Ratchet ended up fused together after a freak accident. They were seperated, but Ratchet wound up seeing (and feeling) what Megatron did.
** Returns in a horrible way in the ''Regeneration One'' comic series, a continuation from where the US Marvel line left off after issue 80. [[spoiler: [[TheBusCameBack Megatron's back]] after [[NoOneCouldHaveSurvivedThat surviving the crash of the Ark off-panel]]. By extention, so is [[TheMedic Ratchet]]. However, Ratchet is [[AndIMustScream confined to a tortuous existence]] a [[LosingYourHead living head mounted on the front of Megatron's battle sled]], forcing Ratchet to watch as Megatron lays waste and [[{{Necromancer}} reanimates dead Transformers]] as zombies.]]
* Back when he was Impulse, [[TheFlash Bart Allen]] acquired the power to create energy duplicates of himself. When one of them died during ''OurWorldsAtWar'' he went into psychic shock. While he recovered, he was extremely reluctant to use the power after that.
* In ''ComicBook/TheSmurfs'' comic book story "The Hundredth Smurf" (and its AnimatedAdaptation), Vanity had synchronized movements with his mirror duplicate until the duplicate got knocked out by running into a wall (or, in the case of the cartoon show, until the duplicate fell down the stairs and out the door of Vanity's house).
[[/folder]]

[[folder:Films -- Live-Action]]
* In the first two Heisei era ''Franchise/{{Gamera}}'' movies, a [[AppliedPhlebotinum bead salvaged from ancient Mu]] psychically bonds a girl named Asagi to the title monster, resulting in her sharing proportional injuries when Gamera is wounded. This bond is broken at the end of the second movie, though in the third the ''enemy'' monster Irys gets [[EvilCounterpart its own psychic partner]].
* The Creator/JackieChan film ''Twin Dragons'' has him playing twins SeparatedAtBirth. They can influence each other's movements... somehow. The specifics aren't ironed out, but examples include Engineer Fighter Jackie finding his fingers tapping oddly while Musician Jackie is playing the piano in concert, and Musician Jackie being able to fight off {{Mooks}} while Engineer Jackie is in a cage because Engineer Jackie starts making the correct punch and kick motions.
* BigBad Prince Nuada and his sister Princess Nuala suffer from this in ''HellboyII: The Golden Army''. This ends in [[spoiler:Nuala performing a HeroicSacrifice by killing herself in order to stop her brother's plans]]. It also makes the HostageForMacGuffin ultimatum the BigBad makes with his sister as the hostage rather stupid. And Abe even [[IdiotBall stupider]] for doing it anyway.
* Played for comedy in Stephen Chow's ''Royal Tramp''. When Stephen finds out they're synchronized, he insists on "testing" them, taking one behind a curtain and leaving the viewer to figure out what he's doing by the reactions of the other one.
* ''Creator/CheechAndChong's The Corsican Brothers'' plays the classic tale for laughs.
* In the movie ''Film/{{Pumpkinhead}}'', those who summon the eponymous vengeance demon feel the pain that the demon causes to its victims, and Pumpkinhead feels the pain caused to its summoner; the only way to kill Pumpkinhead, therefore, is to kill the summoner.
* ''Film/ETTheExtraTerrestrial'': Eliott and E.T.
* In ''The Carpenter'', the ghostly carpenter is pained whenever his house is damaged. He's vanquished when the place is set on fire, which causes him to burst into flames.
* Part this, part MentalFusion is required on the behalf of the pilots in ''Film/PacificRim''.
* The events of ''Film/UpstreamColor'' are driven by the lifecycle of a parasitical organism that creates a psychic link between those it's inhabited.
[[/folder]]

[[folder:Literature]]
* It's one of the major plot points of the ''Literature/DragonridersOfPern'' books: Newly-hatched dragons bond with the candidate they feel the strongest empathic connection to ("Impression"). From then on, the pair can communicate telepathically and influence each other's emotions. If a dragon's rider dies, that dragon will immediately suicide by jumping ''between'' permanently. If a dragon dies, the shock will often kill his rider outright (or in one particular case, leave them catatonic).
* Many examples from Creator/MercedesLackey's ''Literature/HeraldsOfValdemar'' books, the foremost being the telepathic and empathic bond between Heralds and their [[BondCreatures Companions]]. Similar bonds exist between twins (those with mind-magic, anyway) and lifebonded couples.
* The twin version appears in the novel ''The Bumblebee Flies Anyway''.
* Another twin version in ''[[Literature/InheritanceCycle Eldest]]'': When Roran [[spoiler: bludgeons one Twin to death, the other convulses and dies.]]
* One sub-story in ''Literature/AmericanGods'' features a pair of African twins, sold into slavery aged twelve and separated when they're sold on. They never see each other again in the flesh... but when the boy is bitten by a poisonous spider and loses an arm as a result, his sister's arm withers for no reason her owner's doctors can explain. The brother also appears to the sister one last time after his death.
* Also used between the twins in Kate Forsyth's ''Witches of Eileannan'' series; Isabeau and Iseult are psychically linked, meaning that when Isabeau is being tortured, Iseult feels severe pain and passes out. It later comes in useful when Iseult goes into labor.
* Roz Brickman from Patrick Tilley's ''Amtrak Wars'' series shares the injuries inflicted on her brother Steve.
* In one of Creator/TamoraPierce's ''[[Literature/TortallUniverse Protector of the Small]]'' books, Neal forces a cloak on a man that makes him feel the pain of the people he beats after he finds bruises and broken bones all over the man's indentured servant.
* In ''Literature/CircleOfMagic'', Jory says that every twin in the (admittedly magic) world knows where their twin is and if they're hurt. In the ''Literature/TortallUniverse'', when Aly is kidnapped her parents are constantly writing to her twin Alan to ask him if she's still alive, as he would know the moment of her death.
* Creator/DamonKnight's science fiction story "Rule Golden" about an alien who comes to Earth and uses some AppliedPhlebotinum to change all mammals on the planet so that whatever they do to something they also feel. Slap someone and you both feel the pain. Kill someone and you have a heart attack and die. Sit on a hoard of food while other starve around you and feel the pain of their hunger. The title of the story is the reverse of TheGoldenRule, attributed to Jesus of Nazareth in the Biblical book of Matthew: "Do unto others as you would have them do unto you."
* The protagonist of Creator/CharlesStross' ''[[Literature/TheLaundrySeries Jennifer Morgue]]'' is "destiny entangled" with his partner... this grants them useful tricks like telepathy and sensorium sharing (definitely FetishFuel when one half of the partnership is a succubus...) but with the downside that they [[spoiler:eventually lose all individuality and become a single mind in two bodies.]]
* A major point in ''[[Literature/SwordOfTruth Faith of the Fallen]]'' is the so called maternity spell, which causes that effect... useful for taking hostages.
* ''Literature/PercyJacksonAndTheOlympians'': Percy and Grover's empathy link.
* In ''Bronze Dragon Codex'', Tatelyn and Simle get this due to a Starjewel.
* ''Literature/SeptimusHeap'': A sought-for art for Dragon Riders [[spoiler:that Septimus and Spit Fyre use in ''Darke'' to win the duel with Merrin Meredith.]]
* The Elf and panther ''[=ClawBound=]'' pairs in James Barclay's ''Raven'' and ''Elves'' novels are linked in both this fashion and with MentalFusion. Although they don't necessarily die at ''exactly'' the same time, they don't outlive eachother for very long and are always buried together (or left to the rainforest, if they're on their home continent of Calaius).
* [[TheChosenOne Rand]] and his EvilCounterpart [[TheAntiChrist Moridin]] get synced together about halfway through ''Literature/TheWheelOfTime''. The link transmits emotions, physical pain, and occasionally pops them into each other's dreams. [[spoiler: At the end of the series, this leads to a FreakyFridayFlip- Rand is dying, but wants to live, while the suicidal Moridin is still healthy. Their link swaps their minds, allowing Moridin to die in Rand's body, while Rand lives on in Moridin's]].
[[/folder]]

[[folder:Live-Action TV]]
* In ''Series/{{Fringe}}'' a boy becomes synchronized with a fungus. If it dies, he dies, and he senses what it senses (light, heat).
* ''Series/{{Farscape}}''
** An episode features a pair of bracelets that cause one of the wearers to feel what the other is feeling. Even injuries. This is used by the crew as insurance when dealing with Scorpius. [[spoiler: It doesn't work particularly well, as Scorpius threatens to blow up Earth, and is easily tough enough to just throw John around anyway. In fact at one point Scorpius ''stabs himself in the wrist'' to get John to drop a gun.]]
** Later, a greedy doctor purposely synchronizes pairs of Moya's crew so that he can charge them a huge fee for the cure. Which of course [[CarryingTheAntidote only he knows how to make]].
* In ''Series/RedDwarf'', the Justice Field reflects any criminal acts back upon the actor. If you try to light the sheets on fire, you end up lighting yourself on fire (and the sheets stay unburnt). "It's the ultimate deterrent," as Rimmer says. This situation leads to a marvelous fight in which hitting your opponent hurts ''you'' instead. The bad guy, a Simulant (think the Terminator with ''really'' bad BO) [[TooDumbToLive is too dumb to realize what's going on]]. So he tries shooting Lister and throwing a knife at him. Twice. Lister even draws a target on his groin and presents it for kicking. Then he hands the Simulant a few giant vases, to be smashed over Lister's head. The Simulant then tries to strangle Lister, thus strangling himself. With the bad guy defeated, [[{{Cloudcuckoolander}} The Cat]] turns up, armed with a spade...
* In the dramatization of ''Longitude'', one of the cranks seen by the Longitude Committee suggests using a "powder of sympathy" to link dogs in this way. The idea is that a dog on land would be injured at noon each day, causing its counterpart aboard a distant ship to bark in pain. In this way the sailors could keep track of Greenwich Mean Time. Not surprisingly the Committee didn't think much of the idea -- Untruth in Television, you might say. (Of course, they didn't think much of John Harrison's practical methods either.)
* In one episode of ''Series/StarTrekTheNextGeneration'', Capt. Picard and Dr. Crusher are (slowly) synchronized by alien technology implanted into their brains as a prisoner control device (they experience debilitating pain and nausea if separated too far). Slowly because the implants gradually get more effective as they "learn" their hosts' brains. Mostly though, the whole episode is an excuse to get them to talk to each other about their feelings.
* Used in one episode of ''Series/LegendOfTheSeeker''.
* In ''Series/TheVampireDiaries'' [[spoiler:Katherine has a witch create synchronization between herself and Elena to prevent the Salvatores from killing her. They end up stabbing Katherine non-fatally a couple times before being informed about what's happening to Elena.]]
* Multiple artifacts in ''Series/{{Warehouse 13}}'' have this kind of effect.
* The Globbor monster on ''Series/MightyMorphinPowerRangers'' had an energy link to Ninjor, making the Rangers fearful to attack him.
* In ''Series/HerculesTheLegendaryJourneys'', if a person dies or is injured, their MirrorUniverse counterpart will suffer the same fate and vice-versa. [[spoiler: However, if a person is in the void between worlds, only pain will transfer, as shown when The Sovereign is killed, Hercules feels the pain of being stabbed, but survives.]]
* One of the comedy skits from the original ''TheElectricCompany'' had two brothers inflicting pain on themselves that the other would feel until the both of them collapsed.
* One episode of ''Series/{{Charmed}}'' had Phoebe synchronized with a MagicalNativeAmerican man who was trapped in a time loop in an alternate dimension and sentenced to die, something that would kill Phoebe as well.
** Also, most of the TimeTravel episodes had characters (most notably [[spoiler: Chris and Wyatt]]) synchronized to their past-selves so that anything that happened to the past character happened to the time traveler as well.
* In ''Series/{{Haven}}'', the villain William is linked to Audrey, which makes it rather difficult to fight him. On the plus side, he has a HealingFactor, and when he heals, Audrey does as well. At one point, Nathan resorts to knocking her out to defeat him. There is also an amusing scene where Nathan hits him with a GroinAttack, and it ''doesn't'' hurt her.
[[/folder]]

[[folder:Puppet Shows]]
* ''Film/TheDarkCrystal'': The [=urRu=] (Mystics) and Skeksis are connected, so that when a member of one race dies so does one of the other (so their numbers are always the same), and when a Skeksis is injured one of the urRu suddenly sustains an identical injury. The nature of this connection is a subtle clue to [[FusionDance the film's ending]].
[[/folder]]

[[folder:Tabletop Games]]
* ''TabletopGame/{{Warhammer 40000}}''
** [[HumongousMecha Titan]] Princeps suffer physical pain when their titans suffer battle damage. Not merely the Princeps, but the key members of his crew also suffer such pain, in varying degrees, particularly the Moderati.
** In a similar manner to the above, [[HumongousMecha Tau Battlesuit]] pilots suffer from this, including "battlesuit psychosis", in which they are so linked to the suit, so used to it that they cannot function without the suit's sensors as filters for their own senses, and if the suit is damaged, (say by the loss of an arm), the pilot will find themselves unable to use that arm until the suit is repaired. The Tau also have a 'bonding ceremony' which can provide a kind of synchronicity between its members, to the extent that the death of a member of the bonded team can drive the survivors insane (by Tau standards), although the more survivors there are, the less trauma, apparently.
* ''TabletopGame/DungeonsAndDragons''
** Some powers can induce synchronization between two living beings, like the psionic science "Fate Link" or the "Death Link" spell. Both creatures will lose {{Hit Point}}s if one is wounded, but death isn't necessarily automatic for both if one is reduced to zero. Can be useful as a bargaining chip (to dissuade an enemy from getting violent), or to wound a creature otherwise immune to many forms of attack. Can also work in reverse, rejuvenating both creatures by using healing magic on just one. Or, by constructing a triangle of "Fate Links", to mean that any damage to one participant results in [[GameBreaker infinite damage to all of them.]] There is at least one build that deliberately inflicts this on ''themselves''. Combined with the [[ExactlyWhatItSaysOnTheTin "Masochism" feat and "Delay Death" spell]], the character gets a single round with an infinite bonus to all rolls.
** In the ''TabletopGame/{{Ravenloft}}'' setting, Dr. Mordenheim and Adam are linked in such a way that they have to be killed at the same time, else they regenerate from any injury.
** Still with ''D&D'', a minor synchronization also exists between a magic-user and his familiar (or a creature like a homunculus), although the exact effects vary from one Edition to the other. Though it doesn't concern mere wounds, a wizard will suffer badly if his familiar or homunculus is killed, and a homunculus never survives his creator's demise.
** Likewise, the Shaman takes damage when her spirit companion is destroyed, and the companion vanishes if she falls unconscious.
* The Twin Souls merit in ''TabletopGame/MageTheAscension'' lets you combine spheres and boost Quintessence when in contact, and keep track of each other relatively easily when not. On the down side, if one dies, the other must make a tough Willpower roll to survive the psychic shock.
[[/folder]]

[[folder:Video Games]]
* In the ''VideoGame/MegaManBattleNetwork'' series, Lan and his Net Navi [=MegaMan.EXE=] often synchronize with each other.
** A particularly extreme example occurs at the end of ''Battle Network 3'', when Lan [[spoiler: digitizes himself into the net world and literally fuses with [=MegaMan.EXE=] in order to increase the latter's power as much as possible to destroy the BigBad Alpha.]]
** From ''Battle Network 4'' onwards, it becomes a gameplay effect: Damaging enemies just before they attack causes this, which gives you double damage on your next attack. It's even more extreme in the manga, where the consciousness of the Operator and Navi actually merge. In addition, any damage done to the navi in the virtual world is transferred to the operator, be it a small cut, a dismembered limb, or full-out deletion/death. The concept in general is taken a bit further than usual, with Full Synchro being explained as [[TechnoBabble eliminating the delay between a command being issued and it's execution]], which is absolutely necessary to the most powerful of the autonomously operating Net Navis, who don't have such a delay in the first place.
* ''Franchise/StarWars: VideoGame/KnightsOfTheOldRepublic 2'':
** The Jedi Exile is synchronized with one of the characters in their party, causing any status buffs either one receives to affect the other. There is talk of severe consequences to the Exile should the character die, but the game wisely doesn't inflict damage on both characters in combat if one is hit. It is, in fact, a plot point that you do not take damage from the other if it is in the heat of battle.
*** The game makes clear that it is this trope and not just CantLiveWithoutYou by first having a cutscene where harm to the synchronized character causes ''intense'' pain to the Jedi Exile, and then after you've hashed out how the link works having the mentor teach you how to block pain from going one way or the other.
** The bond there was based off a similar (but weaker) bond between Bastila and the player in the first game. That one was not strong enough to serve as a physical conduit, but only served as a plot point to justify a series of HeelFaceRevolvingDoor rotations.
* In ''VideoGame/FinalFantasyIV'', Cecil and Kain murder Rydia's mother by killing her conjured dragon. In the DS remake, Pochika/Whyt is a substitute for the party Summoner, and is thus bound by the same rules. If it dies, she does as well.
* ''VideoGame/BloodlineChampions'' has the Psychopomp's Soul Link ability, damaging and causing an effect on enemies hit to also cause their allies hit by the effect to take an additional 20% of the damage they personally take while the effect is on. The Guardian had an ability called Thrust, which would cause an ally you hit to have part of the damage they take while affected be done to the Guardian, with the damage the Guardian taking from that being also reduced.
* ''VideoGame/TheWorldEndsWithYou''
** The characters ''have'' to synchronize themselves with another player, if they want to win the game. This, however, comes with all of the above explained consequences. This works the same way during battles, as enemies and Players alike share life force on the top and bottom screens. If Neku defeats an enemy on the bottom screen, it is also [[DeadlyEuphemism erased]] on his partner's side.
** In addition, eating food raises the Sync Ratio of your partner (somehow?). The lower the Sync Ratio, the less effective they are in battle, with a 0% sync resulting in insultingly bad performance. Yeah, the more they like the food, the better; they gives audio cues as to how each food item appeals to them. But this is a temporary effect, fading within a few battles; for increased sync that lasts longer, Neku and partner should really wear the same brands.
* The final boss in ''VideoGame/PlanescapeTorment'' is [[spoiler:The Transcendent One, the Mortality of the Nameless One]]. Both it and the protagonist are immortal [[spoiler:due to being separated magically]] and one way to end the game is to [[spoiler:use a weapon that can permanently kill the Nameless One, the Blade of the Immortal, on yourself; this will destroy both of them.]]
* ''VideoGame/MechWarrior'' pilots wear neurohelmets which link their consciousness to their Mechs and lets the Mech use the pilot's sense of balance to keep upright. It also functions as a security system, to prevent other pilots from stealing a Mech. The link is explicitly and wisely not two-way in most occasions, but "neurofeedback" can result from ammunition explosions. It is described as extremely painful, and frequently renders the pilot unconscious from sensory overload. If it happens too much in a short time, it can even kill the pilot, similar to how a strong shock across the heart can stop it.
* In ''VideoGame/{{Metroid}} Fusion'', it's stated that when Samus puts on her semi-organic Power Suit, it bonds to her nervous system, which is why no one can remove her suit but her; this leads to problems when she needs emergency medical attention, like when the X Parasite infect her through the suit. It's also why when she is infused with Metroid DNA to save her life, her suit grows a layer of Metroid flesh; it couldn't be removed entirely and she had to be treated with it on. Fan speculation states her relationship with it may be more symbiotic: it's the reason why she feels pain when her suit is hit, why she regains health if she picks up energy, and why she can go hours or days on end non-stop without rest or eating (she siphons energy from her suit).
* In ''VideoGame/FireEmblemAwakening'', [[spoiler:The [[PlayerCharacter Avatar]] was created as a living vessel for the [[BigBad fell dragon Grima]]. As such, s/he and Grima share the same soul. This becomes important around the endgame, as Naga revealed that her power could only put Grima back to slumber, and the only way for Grima to die is to kill himself. The Avatar can use this to put a permanent end to the fell dragon, but in doing so, [[HeroicSacrifice they would also die.]]]]
* ''Franchise/{{Pokemon}}'':
** Has the ability "Synchronize", which works in that if the Pokémon with that ability gets [[StandardStatusEffects poisoned, paralyzed, or burned]], then their opponent gets poisoned/paralyzed/burned, too.
** There is also the move Destiny Bond. The Pokemon that makes the move places a bond of fainting on the opponent that K.O.'s it on the next turn which makes the K.O.er faint.
* In ''VideoGame/ShinMegamiTenseiI'', the Hero is linked to [[spoiler:the Heroine]]. AfterTheEnd, he remains linked to her reincarnation, and whenever there is a full moon he takes damage from [[spoiler:the fact that a demon is currently devouring her from the inside out]].
* Rynn and Arokh make a "Bond" in ''VideoGame/{{Drakan}}: Order of the Flame'' that effectively synchs their hit points with each other (in-game it is described as "merging their existences into one"). It doesn't seem like a fair trade at first, since Rynn is a mere mortal and Arokh is a [[OurDragonsAreDifferent nigh-unstoppable dragon]] but apparently, only killing Arokh kills Rynns as well, not vice versa. This is also supported by the fact that the human who originally made a Bond with Arokh (a certain Heron) has been dead for centuries when Rynn meets Arokh.
* It used to be in ''VideoGame/SuperMarioWorld'' that [[PowerupMount Yoshi]] eating a powerup would affect Mario. This is not longer the case in ''VideoGame/NewSuperMarioBrosWii'', but in that game, using a held powerup affects all players, unlike powerups found in levels.
* In ''VideoGame/{{Warcraft}} 3'' tauren spirit guides could use spirit link to bind several people together. However it was used defensively, because instead of the damage being duplicated it was split between them, causing an enemy's attacks to be dispersed though a larger group of people and thus easier to keep people alive through.
* In ''VideoGame/WorldOfWarcraft'' it is used both offensively and defensively:
** A Holy Paladin's spell "Beacon of Light" causes any heals they cast to also heal the one carrying the beacon. Protection paladins have an ability that takes part of damage dealt to raid members and transfers it to him.
** San'layn encountered in the Icecrown Citadel have the ability to link two members of the raid, with any damage dealt to one also being dealt to another.
** The Wracked Slaves in Zangarmarsh frequently attack in pairs, with a visible "tether" between the two of them. Any damage inflicted on one is divided evenly between both, resulting in the pair lasting twice as long (but also resulting in both dying at the same time).
* The InteractiveFiction game ''Savoir-Faire'' has a magic system based around linking objects so that what happens to one happens to the other as well. People can also be linked, and it's said that members of feuding aristocratic families are often linked to one another as a sort of hostage thing, so that one family can't harm members of the other without also hurting their own relatives.
* ''VideoGame/BioShock2'' reveals that the first series of Big Daddy would fall into a coma and die if their Little Sister were killed. Or if they just wandered off too far.
** Sofia Lamb actually exploits this, [[spoiler:by smothering (but not killing) Eleanor in front of Delta, fatally injuring the bond between them. The broken bond ends up being one of the contributing factors in Delta's death.]]
* In ''Videogame/KidIcarusUprising'', Dark Pit is connected to Pit, since he's really the physical manifestation of Pit's "dark side" (not that Dark Pit is actually dark - more neutral than anything). When Pit [[spoiler:gets trapped in a ring]] for three years, Dark Pit is unconscious the whole time - so he realizes that he's connected to Pit, much as he dislikes it.
* The Life Link concept in ''VideoGame/BlazBlue''. What makes it unique is that so long as one lives, the other will continue to survive and the only way to kill them is to take out both individuals at the same time. Ragna/Nu-13 and Terumi/Mu-12 are known examples of this.
[[/folder]]

[[folder:Visual Novels]]
* In ''VisualNovel/{{Tsukihime}}'', the maids Hisui and Kohaku are known as Synchronizers. It is known they can give other people energy and maintain their sanity [[spoiler: or remove it little by little...]] Also Shiki and SHIKI in Hisui's route connect during dreams and feel the pain/take the damage of the other. Unfortunately, SHIKI has something of a HealingFactor...
* ''VisualNovel/FateStayNight'':
** [[spoiler:The Shadow and Sakura]]. [[spoiler:The Shadow is actually her subconscious mixed with and powered by the Tainted Grail (most likely, it is a shadow familiar of hers). So although she is usually not actually leaving her room, the Shadow is going out and eating people, providing her with prana. Although, she does go out herself sometimes as well.]]
** [[spoiler:Also Shirou and Archer. Because Archer is the (possible) future version of Shirou, being in the same timeline as his past self causes Shirou to unconsciously leech Archer's power's and skill's. This allows Shirou to gain several [[TookALevelInBadass level's in badassery]] (Although it largely depends on the route.)]]
[[/folder]]

[[folder:Web Comics]]
* Two of the main characters of ''Webcomic/{{Darken}}'', Gort and Mink, share such a bond. Mink is rather annoyed by it, due to Gort's tendency to [[LeeroyJenkins charge into trouble]] with his sword raised, often commenting "He's going to get us BOTH killed!" Gort was the one who agreed to the creation of this link, in order to [[PetTheDog save Mink's life]], and nobody's entirely sure why (since he's basically a supervillain), though allegations of a romantic relationship between the two HAVE been made.
* ''Killroy & Tina'' are linked thus. They also [[WonderTwinPowers share super powers]] as long as they're within five kilometers of each other.
* ''Webcomic/GirlGenius'': Gil and Tarvek wind up synchronized by a "Si Vales Valeo" procedure intended to save Tarvek's life. And then Agatha comes down with the same disease Tarvek has, which means she gets hooked into the procedure as well.
* Happens both ways in ''Webcomic/TheDragonDoctors.'' When Kili's soul is plunged into darkness and imminent death by an evil spirit, her empathically-bonded lover Greg nearly dies along with her, but is able to use his connection to save her and himself.
[[/folder]]

[[folder:Web Original]]
* ''Literature/WhateleyUniverse'' example: Tennyo and Generator are now psychically linked so when one get really badly hurt, the other feels it. Not really helpful so far.
* ''TrintonChronicles'' Aurora is linked to her duplicates the same way by feeling their pain and their death, kind of screws her up mentally.
[[/folder]]

[[folder:Western Animation]]
* Demona and Macbeth from ''WesternAnimation/{{Gargoyles}}'' were synchronized by a magic spell that caused them to feel each other's pain whenever they are in close proximity, implied to be intended to keep Demona loyal as Macbeth's protector. Since they came to hate each other's guts, there has been a series of violent confrontations where they're essentially beating ''themselves'' up by fighting the other. This is the source of their immortality compact, handed out by the mystical tricksters that granted the wish; they cannot die unless one kills the other, at which point ''both'' will. It's seemingly Macbeth's [[DeathSeeker life goal to do just that.]]
* Tomax and Xamot from ''Franchise/GIJoe'' are an example of synchronized twins. It seems to end at pain (and possibly pleasure), though -- Xamot has a facial scar that Tomax lacks.
** Referenced on ''WesternAnimation/FamilyGuy'' when Stewie and Brian pretend to be them.
-->'''Stewie:''' I'm Tomax and this is Xamot. We're twins who can feel each other's pain.\\
'''Brian:''' (''after Stewie steps on his foot'') Ow!\\
'''Stewie:''' No Brian, I'm supposed to say 'ow!' You ruin everything!\\
'''Brian:''' (''after punching Stewie'') Ow.
* In the fourth season of ''WesternAnimation/{{Ben 10}}'', Ben gains an alien form called Ditto that can split into multiple copies of itself, with the catch being that they all think autonomously, albeit with the same personality, but are synchronized so that pain inflicted on one Ditto is felt by the others.
** [[WesternAnimation/Ben10AlienForce Echo Echo]], on the other hand, is essentially Ditto with a [[MakeMeWannaShout sonic scream]] but ''doesn't'' have Synchronization, instead the clones are very fragile.
* ''WesternAnimation/CaptainPlanetAndThePlaneteers'': Captain Planet is synchronized with Gaia (whenever she's hurt, his powers fail). Gaia is linked to the Planeteers (if they turn on her or abandon her, she loses her powers). And of course the whole team is connected through Ma-Ti, and Gaia is synchronized with the whole Earth... oh... as they say on ''WesternAnimation/AvatarTheLastAirbender'', everything is connected. Example: When Gaia temporarily lost her powers, Captain Planet was depowered and couldn't dissipate, meaning that the Planeteers rings didn't work.
* The subject of the ''WesternAnimation/MenInBlack'' episode "The Psychic Link Syndrome".
* ''WesternAnimation/{{Wakfu}}'': Amalia (like any Sadida) is somewhat synchronized with her animated puppet, which she uses to fight (though this doesn't transmit wounds; in fact she can use it as a shield). This turns out quite problematic in episode 7, where Amalia gets poisoned and thus delirious, and the puppet becomes a nasty, evil little pest.
* In one episode of ''WesternAnimation/{{Futurama}}'', Bender feels what Leela feels due to an emotion chip installed.
* In ''WesternAnimation/KungFuPandaLegendsOfAwesomeness'', "Bad Po" has this happen between Po and his EvilTwin, used for genuinely hilarious effect.
* In ''WesternAnimation/TransformersPrime'', Starscream makes an army of clones, only to find out that he feels whatever pain they experience. He discovers this when Bulkhead ''beats one to death''.
[[/folder]]

[[folder:Real Life]]
* [[UsefulNotes/QuantumPhysics Quantum entanglement]]: AlbertEinstein famously derided the concept as "spooky action at a distance". But it turned out that this phenomenon really exists.
[[/folder]]
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