Symbiotic Possession

When a demon (or any other invading, mind-controlling force) possesses someone, it can get pretty nasty. The host will have no control over their actions, they'll be forced to do the demon's bidding, or even fight their former friends. It's not a pretty picture...

...unless the demon and its host are pals.

Sometimes a demon, spirit, or any other entity that is forcefully placed into someone's body (willingly or otherwise) befriends its host, and they form a mutual, symbiotic relationship. Maybe the demon lightens up a bit once his host befriends him. Maybe he realizes that humans in general are all around good creatures that should be befriended, not taken over. Maybe he's not fond of his host, but there's a greater threat that can't be conquered unless they combine their efforts. Maybe he was never evil in the first place, and after being crammed into someone's body against his will, he felt that he might as well make friends with his fellow captive. Maybe they're both evil, and they realize that two evil heads are better than one.

Whatever the case is, the two become less of a parasite and host, and more like two allies in one body. They view each other on equal ground and are willing to pass control of the body between each other when the situation calls for it.

Compare Willing Channeler, when the host willingly accepts the demon into his body in the first place and Heroic Host where the partnership grants fantastic ablities. Contrast with Demonic Possession, when it certainly isn't a fair relationship, and Sharing a Body, for when it's two people in the same body, and not a possessor and a host.


Examples:

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     Anime & Manga 
  • Fullmetal Alchemist has two situations like this in the original manga and the second anime:
    • Greed (in his second incarnation) is born by being injected into Warrior Prince Ling Yao's body. He takes it over, but Ling's mind survives because he willingly allows Greed into him. While Greed remains in control early on, Ling slowly breaks through him. By the end of the series, the two see eye to eye, throwing witty banter between each other and switching off control based on whether Greed's Ultimate Shield or Ling's chi-sense is more useful at the moment, and Greed finally realizes that it was friends that he wanted all along, not 'possessions'. He dies by willingly giving up his life to save Ling's.
    • A case could also be made for Van Hohenheim, Ed and Al's father, who is now merged with over 500,000 souls — all citizens of the lost nation of Xerxes, with Hohenheim as its Sole Survivor. He's gotten to know each and every single one of them over the centuries, and they all agree that they'll take down the Big Bad, the cause of their collective misery.
  • In Naruto, most of the Tailed Beasts are either treated as wild, mindless creatures, or as Chaotic Evil monsters intent on complete destruction. However, Killer B and his companion, the Eight-Tailed Ox, are on equal terms with each other, viewing each other as friends, which makes Naruto want to have the same relationship with his own Tailed Beast, Kurama the Nine-Tailed Fox. He ultimately succeeds.
  • In Vampire Hunter D, D and Left Hand seem to fit the bill.
  • This is a recurring notion in the Yu-Gi-Oh! series:
  • Kurau Phantom Memory: A Rynax is a being from another world; if one comes to our world it needs to find a host (a human) to survive or it will die.
  • Shinichi and Migi in Parasyte ended up this way eventually, although Migi always was rather disagreeable at times. Normally, the aliens take over a person's head, but in this case, Shinichi kept it from moving further up than his arm long enough that it couldn't move anywhere else.
  • In Umi Monogatari, Urin's relationship with Sedna works like this. Urin gets Sedna's powers, while Sedna inhabits Urin's body.

     Comic Books 
  • The various alien symbiotes from Spider-Man all fit this trope to some degree.
    • Venom is a complicated case. Random people bonded with the symbiote usually get completely dominated by it. Eddie Brock appears to fit this trope, but when he's separated from the symbiote his Catholic guilt kicks in and he thinks of it as a curse. Mac Gargan fit the trope, but he was bloodthirsty to begin with so the symbiote's influence didn't really matter other than giving him a taste for human flesh. The current Venom, Flash Thompson, manages to fit this trope through chemical controls and sheer will until the symbiote gets an intervention from its species and has a Heel–Face Turn.
    • When teenager Andi Benton bonds to a Venom clone, becoming Mania, it influences her behavior to a certain extent, but by and large Andi takes to symbiosis like she was born for it.
    • Cletus Kasady, of course, loves being bonded with the Carnage symbiote. They get along so well that they used to be considered one being. Unfortunately, this is because they're both vicious mass-murdering psychopaths.
    • And Toxin. Patrick Mulligan's relationship with his symbiote is best described as parenting.
  • The Spectre is often presented this way, at least when it's established that he and his host are separate entities.

     Fanworks 

     Literature 
  • Animorphs has a few of those:
    • One of the main way for the Yeerk Empire to enslaves human is through the Sharing, a boy-scoutish cult that isolates people in need of acceptance from their peers and "enhance" them by making them Controllers.
    • Also, most Taxxon-Controllers have this relationship with their Yeerks, because it spares them to a degree from their never-ending hunger.
    • Members of the Yeerk Peace Movement argue that this is the only kind of relationship that should exist between Yeerks and hosts, refusing to infest unwilling hosts. The Animorphs' first contacts in the Movement, Illim and Mr. Tidwell, started as master and slave but ultimately chose to Share A Body instead.
    • The Iskoort took this one step further. "Iskoort" is the name for the merger of the centaur-like Isk and slug-like Yoort; the Yoort were Yeerks at one point in their history, until they genetically engineered the Isk to serve as their bodies (kind of like a biological Powered Armor). The Yoort then engineered themselves so they couldn't survive without the Isk, making it a true symbiosis. Part of why the Animorphs are sent to their world as part of the Ellimist's eternal war with Crayak is because, should the Yeerks win, there is a small chance at that some point in the future, the rest of the Yeerks will find their "cousins" and realize there's an alternative.
  • In the last book of The Bartimaeus Trilogy, several demons manage to get themselves summoned inside several power-hungry magicians, upon which they take over their hosts and begin causing havoc. In order to save the world, Nathaniel and Bartimaeus willingly share Nathaniel's body, allowing them to combine their abilities to combat the rogue demons.
  • Rhage and his beast slowly become this in Black Dagger Brotherhood.
  • In the Chalion books, to be a sorcerer you have to have a demon inhabiting your body. Who's in charge depends largely on whose will is stronger; the longer a demon is in the world, the stronger it is and the more likely it is to want to take control. The Bastard (who is, among other things, the god in charge of demons) has his devotees strive to remove demons from sorcerers as quickly as possible, because this is easier and less dangerous. But there are rare cases (less than one per novel) where the demon "merges" with the sorcerer's soul, and their wills become harmonious. These sorcerers are permitted to continue practicing, although the Temple likes to keep a close eye on them.
  • The Demon's Lexicon books are full of straight-up parasitic Demonic Possession which gradually kills the human host, but in the third book in the series, one possessed woman makes a deal that she'll get the days and the demon gets the nights, and the demon begins to appreciate human ideas.
  • The Blackened Denarii in the Dresden Files books vary between virtually full partners (Nicodemus) to hosts that are mere slaves to their demon.
    • Also, Harry and Lash (not Lasciel) eventually come to terms with each other. Too bad it doesn't last.
  • Cormac from the Kitty Norville series is willingly possessed by the spirit of Amelia Parker, a wrongfully-executed Victorian-age wizard.
  • Hal Clement's novels Needle and Through the Eye of the Needle had a boy and a symbiotic alien protoplasm that were like this, until the kid got sick.
  • In the The Skinjacker Trilogy, skinjackers can temporarily possess humans. Most of the ones Allie possesses either don't know she's there because it's so brief, or, if they do realize it, they freak out and try to get her out. When skinjacking a young boy, she gets stuck in his body for a while. He initially is scared, but becomes friends with her. It's her promising to help him with his homework that wins him over.
  • Robert A. Heinlein's I Will Fear No Evil. The relationship between Johann/Joan and Eunice Branca, the former owner of his new body. Later on the soul of another deceased person joins them.
  • In The Host Wanda and Melanie finally become friends after Wanda spends some time with other humans.
  • In Spheres of Influence, Oasis Abrams's body is revealed to carry two minds. In her backstory, the body of one of the minds was dying, and the mind of Oasis Abrams was transferred into the brain of a Hyperion. By the time we meet her/them, their minds have sort of fused, creating a new amalgam personality.
  • In The Entertainer And The Dybbuk, Avrom, the eponymous Dybbuk helps Freddie with his ventriloquism act in return for helping track down Avrom's killer.
  • In The Girl From The Well, one of Okiku's powers is to possess people who are close to death, or who have known death intimately but escaped. At the end of The Girl From The Well, Tark is dying from the woman in black draining his spiritual energy, and Okiku possesses him to save his life by filling the spiritual void in him with her own energy. They're able to coexist mostly amicably, though Okiku's compulsive drive to seek out and murder serial killers causes some tension in The Suffering.
  • The heroes in The Kane Chronicles serve as vessels for Egyptian deities, and although the relationship between god and host can be strained, they're still on good terms.
  • In The Machineries Of Empire, undead spirit of Shuos Jedao is attached to Cheris' mind to advise her as she attempts to take on the Fortress of Scattered Needles, and while she doesn't trust him, they come to a mutual understanding.

     Live Action TV 
  • Stargate SG-1: The Goa'uld are parasitic mind controlling aliens, but a small group of them, the Tok'ra, are this. They share the body with the host and don't take hosts who are unwilling. In return, the host gains accelerated healing, access to the many years of wisdom gained by their Tok'ra, and a permanent conversation partner.
  • In the Star Trek universe, select Trills host a symbiote. The symbiote can live for a very long time as long as it is joined with a host. When a host dies, the symbiote is transferred to a new host. The symbiote carries the memories of the previous host with it. As a result, the new host gets the memories and knowledge from all of the symbiote's previous hosts. This results in a fairly young host having memories of several lifetimes.

    Mythology and Religion 
  • This is actually more or less the goal of Voudoun and similar religions. Practitioners hold rituals where they attempt to become vessels for minor deities known as Loas.

     Tabletop Games 
  • Averted with the Player Characters in Demon: The Fallen. The PCs may mostly be the friendly kind of demon, but they can only escape from hell and enter a mortal's body when their host is near death, either in spiritual (e.g. long-time drug addict) or physical (e.g. comatose or bleeding to death) sense. The human soul gets snuffed out or shunted elsewhere. However, the host's memories and some character traits are partially integrated into the demon's own, meaning that you can have a demon who remembers both being the celestial architect of the North Sea and having grown up as a normal human, studied journalism and raised two children.
    • Played straight as an option in the Demon Player's Guide.
  • Certain merits in Wraith: The Oblivion allow you to have a more cordial relationship with your Shadow, essentially establishing some off-limits subjects in exchange for being easier to possess. At the end of the day, though, the Shadow is still your worst enemy and will plot your downfall. Also, pretending to be "your only friend, the only one you can trust" is a popular tactic for Shadows.
  • In Warhammer 40,000 getting possessed or being turned into a Daemonhost always ends badly for the possessed, even if they are Chaos Space Marines. The possessed typically rapidly mutate, go insane, and typically have a very short lifespan, the most notable being Possessed Marines. The host and daemon establish a win-win solution; the host most likely being an Ax-Crazy Blood Knight, the daemon gives them claws, strength, or whatever for the host to kill better, and both enjoy the ensuing slaughter.

     Video Games 
  • In Breath of Fire IV, Ershin and Deis gradually become this.
  • Occurs twice in Devil Survivor. Once with Mari, who allows Kresnik to possess her to destroy its mortal enemy Kudlak and Remiel!Amane
  • In Middle-earth: Shadow of Mordor, the Wraith Celebrimbor possesses the Ranger Talion. The two have a cordial relationship, a shared goal in crushing Sauron, and the Wraith gives Talion a host of supernatural powers to help accomplish those ends.
  • This eventually becomes the relationship between demon Nemissa and human Hitomi in Soul Hackers. The two bicker a lot during the beginning of the game, but they start to develop a mutual friendship as it goes on, with Nemissa allowing Hitomi to get control over her body again from time to time.
  • Shura from Soulcalibur IV. She's just looking for a good fight against anyone who is worth killing, the demon that possesses her is searching for the perfect host to inhabit so it can return to life. It is this unison that bolsters their power when in battle, although Shura is not the body the demon is looking for. As she is trying to satisfy her bloodlust, Shura doesn't mind this arrangement one bit.
    • Natsu (Taki's disciple) in V. She has a great demon known as Arahabaki sealed inside of her, but is apparently on good enough terms with it to call upon its power during her Critical Edge.
  • An odd play on this, Lambda and Richard in Tales of Graces get along just fine...because they both want to eradicate humanity. However, that is eventually revealed to be more of a case of More Than Mind Control, but Lambda and Asbel play it straight.
  • Wynne of Dragon Age: Origins has a symbiotic relationship with the benevolent Spirit of Faith possessing her. She provides it a host body in the physical world, and it's kept her alive since she was killed protecting the child mages of the Circle from a demon. Anders of Dragon Age II attempts this with a Spirit of Justice, but it doesn't go well....
  • Wild Flower of Jade Empire is quite fond of her "guardian" Chang-Ka, a big, shaggy, and (mostly) benevolent demon. Chang-Ka is also fond of the little girl. He needs a tie to the mortal realm to help the Spirit Monk, and she actually died in a flood. He resurrected her to be his host. It's the other demon that's inhabiting the girl that they'd both like evicted.
  • This happens in the Villainous Friendship kind of way if you choose the Demon Path in Soul Nomad & the World Eaters.
  • Skullgirls' Filia appears to regard her hair-parasite Samson in this way, judging by her in-game lines and personality. The amnesia probably helps. However, it's unclear as of yet whether Samson views Filia with the same respect.
    • On the other hand, Squigly and Leviathan have this kind of relationship, and their mannerisms and the fact that Leviathan has been serving Squigly's family for generations show that the feeling is mutual.
    • Eliza and Sekhmet are so far into this trope that they've essentially become the same person. Eliza's story mode doesn't even bother trying to distinguish the two whenever they talk, simply calling them "Eliza".
  • Xenoblade has a Walking Spoiler one between Fiora, a girl assumed dead, and Meyneth, the benevolent goddess of Mechonis. At first only Meyneth has control over the body, but she can still feel Fiora's cries to protect her friends, and does everything in her power to do so. After Fiora's soul recovers control of her body, she's thankful of Meyneth, and wishes to continue with whatever objective Meyneth had set to while she had lone control.
  • In Star Ocean: The Second Story, Ashton ends up in this predicament thanks to the party distracting him before he could finish off a two-headed dragon, which proceeds to fuse itself to his back for the sake of self-preservation. The two quickly take a liking to him and the rest of the party and prove to be helpful in combat, though their tendency to bicker with each other is a source of irritation for their host, who ultimately decides against removing them when he learns the process would kill them, having grown similarly fond of them in meantime. They only take control of him on one instance to say something important (Namely, their realization that they had been longing for companionship all along).
  • In Shadow of the Colossus, Dormin possesses Wander after the latter is fatally injured, keeping him alive and saving his life. Unfortunately, the antagonists manage to screw things up...

     Webcomics 
  • In The Dreadful, Erin and Ith have this kind of relationship.
  • In Drowtales this is the ideal relationship between a drow and any demon they have been "tainted" with, either accidentally or on purpose, resulting in red eyes. Most tainting cases are not like this and involve the host gradually succumbing to the demon until they lose their sense of self entirely and become a rampaging monster, but this trope can occur either through a ritual designed by the instigator of the tainting epidemic or rare cases such as Kiel'ndia where this happens naturally. Visually "merged" tainted are distinguished by having white spirals as pupils, but it's not certain if other characters are able to see this or if it's solely for the benefit of the audience.

     Web Original 
  • In A Very Potter Musical, Voldemort and Quirrel evolve into this.
  • Stalker in Tasakeru is an example of this. He owes his "rebirth" to a fusion between his dying body and that of an infant spider.

     Western Animation 
  • In Wakfu, Sadlygrove normally keeps the demon Rubilax trapped in his sword. Rubilax occasionally manages to possess Sadlygrove and wreak havoc, but when a serious situation forces them to cooperate, Rubilax possesses Sadlygrove to grant him Super Strength, but leave Sadlygrove in control of his body.
  • On Avatar: The Last Airbender and The Legend of Korra, Raava the Avatar Spirit moves from host to host over the centuries. As The Chosen One, the host (known as the Avatar) doesn't volunteer to channel Raava; each Avatar merges with her upon birth. As the Avatars grow up, they learn to work with Raava by harnessing their Elemental Powers and fulfilling their duties as the bridge between Earth and the Spirit World.

http://tvtropes.org/pmwiki/pmwiki.php/Main/SymbioticPossession