Residual Evil Entity

Good triumphs over evil, or evil makes a Heel–Face Turn, at which case the evil "essence" escapes to create some new entity entirely.

Evil is often compared to some sort of tarnish, corruption or filth. Even when they're Character Flaws and not necessarily a physical thing, every evil act, evil thought, or evil trait a person has will take root in the person. Later, the person may become The Atoner or go through some sort of Redemption Quest. Or someone else may defeat them and attempt to purify the evil. But, taking this analogy to its literal conclusion, dirt and grime don't simply "vanish" after being washed off, and still must be disposed of carefully and properly.

So if evil is filth, and goodness is cleansing, where does the evil residue go?

In some cases, it forms a mind and/or body of its own. In others, it joins some greater entity which will exist As Long as There Is Evil. If it's particularly strong or embedded in a person or the world, it may be impossible to get rid of entirely and fester like a boil ready to burst at the slightest Moment of Weakness. In some cases, the entity created may not be Made of Evil itself but was nonetheless created by the prior act of purification.

This plot element typically leans towards the cynical end of Sliding Scale of Idealism vs. Cynicism, at its worst arguing that no problem can ever truly be "fixed" or "settled" and that no person can ever truly be "redeemed". It's also greatly related to the idea of Balance Between Good and Evil because it argues that every victory good has against evil makes evil come back stronger or in some unpredictable form. Which, may also imply that good versus evil is a dance of equal-but-opposite reactions.

Depending on how a work or audience looks at it, this plot point could either discourage complacent behavior by emphasizing that heroes must be ever vigilant or encourage such complacency by convincing them that sometimes it's better to do nothing at all. Sometimes, the problem isn't that evil was purged, per se, but the methods the heroic characters used to do so, which may have been flawed, too easy, or both.

Related to Evil Only Has to Win Once, if good doesn't have the same benefits and once it's corrupted/defeated, it's gone forever.

Compare Evil Power Vacuum. Not to be confused with Resident Evil. Sometimes related to You Kill It, You Bought It, when killing the Evil Overlord turns the person into the new one. See also Post-Mortem Comeback for when the residual evil allows a villain who was destroyed to carry on his work without actually returning to life.

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Examples:

Anime & Manga

• Bakemonogatari: The Monogatari series has a recurring theme that simply defeating evil or malevolence will not get rid of it unless the very root of the problem is cured. And in many cases, a problem rooted that deep in the first place is far beyond the understanding of your typical human (supernaturally gifted or not) to deal with. As such, several arcs in the later parts of the series deal with problems that are recurring because the root issue wasn't solved, or causing an entirely new problem in the absence of the old. One of the wiser, more worldly characters bluntly makes the suggestion that doing nothing and letting the people suffering from a problem deal with it themselves or die trying is usually the better option. And in some cases, later events prove him correct.
• Digimon:
  • Digimon Frontier: In the penultimate battle, the Digidestined battle Lucemon, the Big Bad of the series. When he is defeated, the Digidestined absorb his Digicode/Fractal Code, but only the light half. The dark half, now unfettered by the light, grows and forms into the purely-evil Lucemon Shadowlord Mode.
  • Digimon: The Movie: Diaboromon, the main villain of the Our War Game act, is destroyed by Omnimon. However, the virus that created him lives on and corrupts the Digimon partner of an American Digidestined Willis.
• Dragon Ball:
  • The unnamed Namek that traveled to Earth and studied under the previous God (Kami) of the planet was unable to attain the position himself until he purged himself of evil. He did this by diffusing himself into two entities: one pure good and the other pure evil. His pure evil side, now dubbed Demon King Piccolo, was later sealed away to prevent him from terrorizing the world, and he escapes during the events of the series. Over the course of the manga, it requires Piccolo dying, being reincarnated, adopting his own pupil, sacrificing his own life and being wished back, and becoming friends with the protagonists to suppress his evil side enough for him to merge back with his other half to form a whole, benevolent Piccolo. And even then, there's a tiny amount of evil that he must keep suppressed.
  • After promising his best friend, Mr. Satan, that he would never do anything evil again, Buu is overcome with rage after Mr. Satan and his puppy are shot by murderous human beings. Unable to reconcile his murderous rage and the promise, Buu involuntarily splits into a Good Buu and an Evil Buu. The Evil Buu continues to be a threat until it is destroyed by Goku and then reborn as an ordinary human, as per Goku's request.
• Curses of Jujutsu Kaisen come into existence from "cursed energy", which is basically all the spiritual nastiness that tends to accompany human population. Then they usually stick around until they are either exorcised by a sorcerer or get on the bad side of a stronger curse.
• Kyo Kara Maoh!: after The Great One defeated the Originators, the remnants were sealed into four Forbidden Boxes, and tainted The Great One himself until Yuuri arrived on the scene to finish the job.

Comic Books

• Marvel Universe:
  • The Infinity Saga
    • The Infinity War: It is revealed that in the previous storyline, Adam Warlock subconsciously used the Infinity Gauntlet to purge the evil from his soul. That evil had since manifested as a purple-skinned Evil Doppelgänger of him named Magus.
    • The Infinity Crusade: In the third part of the trilogy, it's revealed that Warlock also created a "good" side named Goddess, who is actually just as dangerous and troublesome as Magus, as her definition of good is "eliminate free will".
  • X-Men: Professor Xavier once used his psychic powers to purge Magneto's mind of evil, leaving him with a more benevolent amnesiac personality. It's later revealed that the evil side of his mind went into Xavier himself, forming an entirely new entity and kickstarting the Onslaught saga.
  • Defenders implies that all of the various primordial dark entities that have plagued the Marvel verse, such as Knull and the Chaos King, were born from the shattered fragments of Anti-All, a draconic embodiment of the void that was defeated in a previous incarnation of the universe.

Fan Works

• Story Shuffle: In "Necessary Evil", the regenerative indestructibility is why the Evil Attractor of the Hollow Shades is necessary. An In-Universe hypothesis is "By removing the Shades, Celestia might be inflicting their darkness on the rest of Equestria." and so she stays her hand. As said by Celestia at the end:
  Celestia: "There is a darkness there greater than any it attracts, one that befouls the very land. I did try to destroy it once. It dodged, and then it moved north. The Badlands were not always such. I thought it better to let that corruption rest where it now lies than to rouse it again."

Films — Live-Action

• The Babadook: After being cowed into submission by Amelia and defeated, the Babadook does not die or go away but instead takes up residence in her basement where it remains weakened and subsisting on worms. Given that the creature is a manifestation of Amelia's depression and grief, which can be controlled and lived with but never truly vanquished, this makes all kinds of sense.

Literature

• Doctor Who New Adventures: A theory about the origin of the energy monster featured in Nightshade is that it's all what's left of a race the First Doctor defeated in the Doctor Who Missing Adventures book Venusian Lullaby.
• Sausagey Santa: The titular character used to be a malevolent Child Hater who was condemned to the Ironic Hell of giving gifts to children for all eternity. He hit on the bright idea to have all evil extracted from him so that he could enjoy being altruistic. Unfortunately, his evil transformed into his arch-enemy, Frosty the Neo-Nazi Snowman.
• The Stand: Randall Flagg, the dark man, vanishes in the nuclear destruction of Las Vegas, ending his fledgling evil empire... until he wakes up on an island surrounded by natives, introducing himself as Russell Faraday and claiming he's come to teach them how to be civilized.
• The Unicorn Chronicles: As revealed in Dark Whispers, the unicorns forcibly removed their flaws and negative traits. Unbeknownst to them, said flaws and negative traits coalesced into an intangible entity, the Whisperer, which manipulates and corrupts other beings, among them further driving Beloved to evil and turning a group of dwarves into the Delvers, who hate unicorns because of the Whisperer's negativity.

Live-Action TV

• Power Rangers Beast Morphers: It's revealed that Evox is actually Venjix, the Big Bad of Power Rangers RPM, reborn. At the end of RPM, Venjix hid within the Red RPM Ranger's Cell Shift Morpher, which was acquired by Grid Battleforce, during which an experiment conducted by a young Nate caused his data to be merged with snake DNA, reviving him.
• Star Trek: The Next Generation: In "Skin of Evil", on an uninhabited planet, the Enterprise crew encounters Armus, a being that looks like an oil slick. It says that it is the result of a process that the original inhabitants of the planet used to shed all of their negative traits. It acts in a capriciously evil way, including murdering Tasha Yar.

Myths & Religion

• Japanese Mythology:
  • In Shinto creation myth, the god Izanagi returned from the underworld after a failed attempt to rescue his deceased wife Izanami and cleansed himself. The gods born from this, Amaterasu, Tsukiyomi, and Susanoo were not evil per se, but are decidedly three of the most powerful and influential in all of Shinto belief.
  • In general, physical and spiritual impurities are called "kegare". In Shinto doctrine, they must be washed and/or purified through specific rituals called misogi and harae. There are also many Japanese Yōkai, or spirits, which are cast-offs or byproduct of other oddities which may not have been dealt with properly or at all.

Tabletop Games

• Advanced Dungeons & Dragons module I10 Ravenloft II: The House on Gryphon Hill. The Alchemist, a.k.a. Count Strahd von Zarovich, creates a device that extracts all of the evil in him and sends it to another plane of existence. The evil becomes a monster known as the Creature, which returns and plagues the Alchemist.
• In the Magic: The Gathering Innistrad set demons cannot be permanently killed: fell one and it reforms elsewhere in some capacity unless some non-planar factor (i.e. Liliana's veil magic or Emrakul's corruption) offs them. This is exploited by the angel Liesa whose pact with a demon allows her to reform in the same way.

Video Games

• Castlevania: Aria of Sorrow: Dracula was Killed Off for Real in 1999 by sealing away his castle inside an eclipse, separating him from the source of his power. Unfortunately, that power still resides within the castle and is seeking a new master to connect to. Graham Jones, believing himself to be Dracula reborn, tries to claim this power for his own, but it turns out that the protagonist Soma Cruz is Dracula's actual Reincarnation. Both Soma and Chaos realize this in the true ending, so stopping it from corrupting Soma and making him into the new Dark Lord forms the climax of the game.
• Castlevania: Lords of Shadow: The titular Lords of Shadow are three malevolent supernatural beings that have plunged the world into darkness. In the end, it's revealed that they are the evil aspects of the Brotherhood of Light's founders, which they had cast away from themselves in a ritual that would give God the upper hand in his war against Lucifer.
• Danganronpa Another Episode: Ultra Despair Girls: The Servant actively strives to avoid leaving any lingering despair, and formulates a scheme to Start X to Stop X by creating as much despair as possible so it will be annihilated once and for all when hope triumphs. However, given that he's Brainwashed and Crazy and a member of Ultimate Despair, his plan is insane and guaranteed to fail.
• Disgaea 5: One of the post-game stories shows that the malicious side to Void Dark wasn't fully purged when Killia hit it with Macrocosm. In fact, the story implies that Void's Malice is gaining a resistance to the skill. Ultimately, it takes a Double Macrocosm from Killia and a now reformed Void to finally vanquish it. However, it still survives and ends up being banished to the Carnage Dimension, where it ends up being the final challenge of the Carnage questline.
• Zemus, the evil puppetmaster behind the events of Final Fantasy IV, willingly allows himself to be destroyed just before the Final Battle. Out from his corpse comes Zeromus, an incarnation of his hatred far more powerful and dangerous than the sorcerer himself could ever be.
• Final Fantasy XIV: Light and Darkness exist in a cosmic balance where neither can ever truly be "destroyed", but defeating or vanquishing a vessel for either will cause the force that possessed it to go somewhere else, and often reach critical mass where it threatens to become more dangerous than ever. This, for example, is the main problem with defeating Lightwardens in the Shadowbringers expansion; whenever one is defeated, the light inside it has to go somewhere, and the most convenient host is usually the being that defeated it. Those that possess the Echo are seemingly immune to this. But really, they're merely more resilient. After defeating several Lightwardens, the Warrior of Darkness starts being overwhelmed by the light energy entering their body, threatening to turn them into an apocalyptic Super-Warden. The Precursors that inhabited the star long before recorded history possessed such powerful mana and magical abilities that containing it would have been easy for them, and the Big Bad, Emet-Selch, wants to see if the Warrior can handle it to see if mortals are worthy of existence. When they fail, he is disappointed, and decides to let them succumb, although his plan later fails.
• Kingdom Hearts: This is more or less what defines the Heartless, Nobodies, and Unversed. The games are not explicitly clear about it, but it's known that if a person "loses heart" or has darkness consume them involuntarily, it turns them into a Heartless. The part of them that's left over without the heart form a Nobody, and Unversed are also somehow connected to despair and negative emotions. Even if someone who lost their heart and became a Heartless regains it (as is the case with Sora), the Nobody they created will still exist.
• Demon King Demise, the Predecessor Villain of The Legend of Zelda series, lays a curse on the reincarnations and descendants of the knight and princess who bested him. At the very least Ganondorf, if not every other Big Bad of the Zelda universe, are incarnations of his hatred.
• In the backstory to Return to Zork, evil magic became so prevalent that an emergency council of wizards and mages teamed up to disperse all magic, resulting in a cataclysm known as the Great Diffusion. That way, when magic finally returned centuries after all the evil wizards in the land had died of old age, the Long-Lived Trembyle and Canuck could restart the practice of magic without any negative influences. Unfortunately, the evil magic wasn't completely destroyed, but merely seeped into the soil until it settled in a deposit of Illuminyte known as the Cluster... which became a bit of a problem when the Dwarves started mining it. The Cluster eventually gained a malignant intelligence, renamed itself Morphius, possessed Canuck as a henchman, began stealing personality traits from its victims, and eventually carved out a new Underground Empire through slave labor - becoming the Big Bad.
• Soul Series: This is a recurring problem when trying to defeat the demonic sword Soul Edge. Its evil is so strong that merely coming into contact with it can corrupt the other person unless their will is exceptionally strong. Any evil or malice in that person's soul is not only fuel for Soul Edge, but can also help it malfest other beings. Case in point, when Siegfried finally overcame Soul Edge enough to try and destroy it with use of the Soul Calibur, this merely resulted in the creation of a separate Nightmare entity for Soul Edge to embody, with no need for a host anymore.
• Street Fighter:
  • The storyline of the Satsui no Hadou (Dark Hadou) introduced this concept with Kage in Street Fighter V. Originally, the Hadou was simply described as a desire to win and destroy one's opponent at any cost, a subconscious desire felt by series protagonist Ryu. Over the course of the series, the Hadou became a more demonic force that could possess and mutate those susceptible to it, and after Ryu finally purges himself of it in V, the evil he cast aside manifests itself as Kage—a much more demonic Ryu.
  • An inverted example was once demonstrated in Bison's origin, which stated that Rose was the physical manifestation of the good that Bison had cast aside in order to perfect his evil power. This plot point, though not retconned, has been downplayed in later games to the point that it's unknown if it's still canonical.
• In Tales of Zestiria and Tales of Berseria, Malevolence is capable of corrupting any living being that comes in contact with it. The major revelation of Berseria is that "malevolence" is born from the darkness in every negative emotion felt within the human heart. In Zestiria, is the Shepherd's job to purify the malevolence from its victims. However, even the Shepherds themselves are not immune to its corruption. This all stems from a curse made by the Original Seraphim in the hopes of proving its fellow Seraphim that humans and Seraphim can't coexist.
• Ultima IX: It's revealed in this game that the Guardian is the evil half of the Avatar, which he/she purged in order to become the Avatar in the first place. The game makes the argument that by becoming the Avatar, he is directly responsible for all of the misery and destruction the Guardian has wrought on every world he's conquered.
• Xenoblade Chronicles 3: Future Redeemed offers a sci-fi spin: While Zanza is dead before any of 3 begins, his despair for the world and desire for its death and rebirth were imprinted onto Ontos, a living supercomputer processor susceptible to his will. Under the new title Alpha, Zanza's malice influences Ontos into becoming a copycat of the destructive god.

Western Animation

• The Fairly OddParents!: In "Vicky Loses Her Icky", Timmy wishes Vicky would be nice, and her evil is released as a bug that begins to search for a new host. Eventually, the bug tries to take control of the United States President to use his resources to destroy the planet and Vicky lets the bug possess her again to prevent this outcome.
• Johnny Test: In "The Good, the Bad & the Johnny", Susan and Mary decide to remove Johnny's bad gene in order to make him nicer. However, events lead to the extracted bad gene growing and gaining a life of its own, resulting in a 100% bad Johnny running around Porkbelly pulling increasingly dangerous pranks. Fortunately, the girls and Dukey manage to capture the bad Johnny and merge it and the good Johnny back into one, with Susan and Mary learning to accept all parts of their brother and Johnny learning to try and be a better person.
• My Little Pony: Friendship Is Magic: In "Castle Mane-ia". the characters discuss the Pony of Shadows, a sort of leftover of evil energy that got left behind when Nightmare Moon was defeated. However, while a glowing-eyed shadow in pony shape is seen lurking in the castle at the end of the episode, the concept of the Pony of Shadows is later retooled in the Season 7 finale to be an independent villain that was Sealed Evil in a Can before Nightmare Moon ever came into being.
• The Real Ghostbusters:
  • In "Robo-Buster", when a rival-made Ghostbuster robot uses overpowered blasters to disperse ghosts instead of capturing them, the dispersed ectoplasm concentration goes beyond critical mass. Cue a city block-sized ghost.
  • In "Citizen Ghost", Peter stores the uniforms soaked in Gozer's psychokinetic marshmallow fluff next to the Containment Unit, which still has a leak in it. The leaking ectoplasm combines with the residual energy in the uniforms and the psychic imprints left by their wearers, i.e. The Ghostbusters, to create spectral versions of the team.
• Rick and Morty: In "Rest and Ricklaxation", Rick and Morty visit an alien health clinic where they undergo a detox treatment that removes the toxic qualities (defined here as whatever parts of themselves the two consider to be "toxic") from their minds and personalities. While at first this appears to simply result in a healthier, calmer duo, the toxicity removed from their minds coalesced into toxic versions of themselves within the containment tank where the toxic cast-off from the process was kept. Toxic Rick becomes an Enemy Without to Healthy Rick once he manages to escape from the tank, although Toxic Morty is much more ambivalent towards his own counterpart — in fact, Healthy Morty is much more actively evil than Toxic Morty is, as Morty considers his dependency on others to be a bad trait and its removal turned Healthy Morty into a manipulative sociopath.
• Samurai Jack: At some point in the very ancient past, an unnamed primordial entity of immense power and malevolence attempted to consume the universe. It was destroyed by the gods Odin, Ra, and Rama before it could do so, but a single sliver of this entity escaped and crash-landed on Earth, where it took the form of a tar-like pool of Ominous Obsidian Ooze that devoured any living creature that touched it. When the Emperor attempted to destroy the evil with an enchanted arrow, he instead caused it to gain sapience and become the series' main villain, the demon Aku.
• World of Quest: The episode "Mirror Quest" has Quest being split into a good and evil version of himself, with the evil Quest going on to defeat Spite and his henchmen and becoming the new leader of Spite's army with the heroes trying to find a way to stop him. Fortunately, the good Quest manages to apprehend his evil self long enough for Anna to merge them back into one.

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