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->''"The Dark Arts are many, varied, ever-changing and eternal. Fighting them is like fighting a many-headed monster, which, each time a neck is severed, sprouts a head even fiercer and cleverer than before. You are fighting that which is unfixed, mutating, indestructible."''
-->-- '''Professor Severus Snape''', ''Literature/HarryPotterAndTheHalfBloodPrince''

%% One quote is sufficient. Please place additional entries on the quotes tab.

If the forces of evil didn't constantly mutate and get better at what they do (fight, steal, sabotage, blackmail, or whatever), the forces of good would've destroyed them eons ago. Simply put, evil, its shape, forms, powers and so on are dynamic, constantly changing and subject to survival of the fittest. This is what TheSocialDarwinist is talking about, and it's definitely what the EvilutionaryBiologist is going to use against you. If you're lucky, they'll [[EvolutionaryLevels evolve according to a predictable pattern]] and you'll be able to anticipate any changes in tactics and equipment you'll need.

Most bad guys are content to evolve by normal Darwinian means, but some guys like to [[CannibalismSuperpower eat things and absorb their DNA]]. Sometimes, there is an entire race of beings that can do this. [[AlwaysChaoticEvil And they all do.]] If you ever find a race like this, [[ViolenceIsTheOnlyOption add them to the list of species that have gone extinct because of man by any means necessary]]. Trust me, no one will miss them.

While good guys in general view this as a cosmic cruelty, the hero with a SuperpoweredEvilSide will be thankful for this, as it will also make him subject to this evolution and therefore he will also constantly get stronger. However, that's not good news if your evil side is the type that tries to take over your mind.....

Sure, good will also change, but in a more 'upgrade' like fashion, giving the bad guys periods between upgrades, during which they have the edge.

This trope presents an interesting inversion to the SortingAlgorithmOfEvil. Compare AdaptiveAbility, see also AsLongAsThereIsEvil. Contrast EvilIsSterile.


[[folder:Anime and Manga]]
* Naraku, the main villain of ''Manga/InuYasha'', is constantly adding new demons to his body, which is the bodies of hundreds of demons thrown together in a blender and solidified.
* The Hollows of ''Manga/{{Bleach}}''. By eating other hollows, they gain power, and evolve through a [[EvolutionaryLevels distinct series of forms]]. Ichigo's inner hollow has also gotten more powerful between the instances we see him.
** Sosuke Aizen tried to weaponize this by fusing the Hogyoku to his chest and wishing it to evolve him into, as he put it, a "being that transcends Shinigami and Hollow". Fortunately, the Hogyoku didn't do what he thought it would.
* While the Kyuubi isn't getting stronger, the seal holding him inside Manga/{{Naruto}} was getting weaker, and more and more tails popped out everytime his power was used.
** More overtly, there's the Juubi (Ten Tails). Before it is sealed into a [[SealedInAPersonShapedCan Jinchūriki]], it handily averts BishounenLine, starting as a vaguely-humanoid statue before its awakening and becoming more monstrous and more destructive with each following transformation.
* Frieza from ''Franchise/DragonBall'' goes through three transformation sequences before reaching his ultimate form. Even then, he gets a power upgrade later on by becoming a cyborg, though this does surprisingly little good as he gets prompty curb stomped almost immediately afterward. On the absorption side of things, Cell and Buu (especially Buu) also qualify as this trope. Interestingly, in Buu's case, the last form fought was also its original one, making it an aversion, at least at the end.
* The Akuma of ''Manga/DGrayMan'' have multiple evolutionary levels. The main character kills a level 1 Akuma in the first chapter. In an early arc two exorcists have trouble facing one level 2 Akuma. The heroes are now facing level 4 Akuma (albeit with difficulty)
** In the Manga this is the explanation for the demons- that were creatures who absorbed other creatures gaining more and more abilities while becoming more and more monstrous.
* Ordinary ghouls from ''Manga/TokyoGhoul'' are dangerous enough that only the most badass humans wielding the bleeding edge technology weapons are able to stand against them. However, would one start to [[CannibalismSuperpower eat other ghouls bodies]], they'd develop [[OneWingedAngel kakuja]], an ability to form armor and enhance their already-existing biological weapons. It also makes them [[WithGreatPowerComesGreatInsanity unable to control themselves]] until they'll eat enough ghoul meat to stabilize kakuja. Needless to say, besides one particular organization there are not that much people who like them among both humans and ghouls.

[[folder:Comic Books]]
* The Brood from the MarvelUniverse are giant wasp-like aliens. Their Queen lays eggs inside their victims, which keep their hosts alive until they hatch. When this happens, the host and the symbiote merge into a fully grown Brood with the host's special genetic abilities. The process is almost flawless, as the Queen was very surprised when Wolverine's HealingFactor kills the symbiote she implanted in him.
* As a meta-example, many villains evolve throughout the decades to better reflect their adversaries and the time. ComicBook/LexLuthor has gone from foreign dictator to insane scientist to politician to business man to reflect the changing views of society and many of Batman's villains have ceased to be gimmicky tricksters and evolved into dark and insane psychopaths. In the Dark Knight ComicBook/TheJoker himself is described as a terrorist, playing on the recent fear of terrorism striking the west over the the last decade.
* some time after ComicBook/TheDeathOfSuperman it's revealed that Doomsday, the monster from that story, has this as a superpower: he revives and evolves immune to anything that killed him before.

* Discussed in ''Film/BatmanBegins'', where Jim Gordon mentions some of the advances Gotham's criminals have made to keep ahead of the police... and wonders what they'll become to counter Batman. [[ComicBook/TheJoker He gets his answer]] [[Film/TheDarkKnight one movie later]].
* This happens in ''Film/PacificRim'', where Kaijus become bigger, more intelligent and more dangerous to counteract the [[HumongousMecha Jaegers]] killing them.

* The Vord in the ''Literature/CodexAlera'', which have an annoying habit of coming up with new forms to counter anything they're faced with.
* In ''Literature/TheDresdenFiles'', older people and beings change less. Older wizards are more set in their ways, and the big supernatural baddies tend to be ''thoroughly'' old-school and anti change. As Harry explains to Butters when the ME finds [[SwordFight "a knife wound, but bigger"]], the White Council is "old school. Really, really old school."
** In the few aversions (Lara would be a monster/being aversion and [[spoiler: Luccio]] is initially a partial aversion, but that turns out to be a big clue), it's always significant. Harry notes that he's often beat the monsters because he can change and they can't, and [[OhCrap without that advantage...]]
** Harry kills [[spoiler:Duchess Arianna]] this way, as she couldn't adapt to the terms of the duel that limited her (otherwise very effective) tactics.
** Not keeping up with things like GPS, gas stations (as combustible locations), kevlar, and other relatively mundane subjects have given Harry a vital edge on several occasions.
* In the ''Franchise/StarWars: Literature/RevengeOfTheSith'' novelisation, Yoda's thoughts during his duel with [[BigBad Palpatine]] are shown to be his realisation that this is why the Sith have won; they had spent the last thousand years (starting with the institution of the Rule of Two) waiting and adapting to the changing Republic, until the moment was right to subtly install themselves in control, whereas the Jedi had not changed (and had probably become even ''more'' rigid in their conservatism and orthodoxy) and were essentially only suited for fighting the last war. This is why Yoda fled the battle and decided to do something more unconventional with regards to Luke.
* The quote from ''Literature/HarryPotter'' refers to the Dark Arts in general terms. Before Voldemort came along, Grindelwald was considered the most dangerous wizard in existence (being that he had the Elder Wand). In a way, the Dark Arts are like an EvilPowerVacuum, with a greater dark force replacing the one that fell. Of course, [[FridgeHorror based on that logic, there's a chance a more terrible wizard than Voldemort will rise.]]
* The aliens in Creator/RobertAHeinlein's ''Literature/ThePuppetMasters'' are scary good at this. Since they can occupy and invade human minds, whatever adaptations humans make to combat them are quickly discovered, and the aliens immediately counter-adapt. It soon becomes clear that the more adaptable species is going to win, and the other is going to be extinguished.
* In the ''Dreamers'' books by Creator/DavidEddings, the Vlagh is an insectoid MotherOfAThousandYoung who is endlessly improving her designs, creating minions for specialized roles [[spoiler:like [[TheyLookLikeUsNow infiltration]]]] and resolving weaknesses as she becomes aware of them. "Evil" being relative, since she's currently stuck in [[{{Mordor}} a wasteland]] and wants her children to enjoy the resources that those pesky humans have been hogging for themselves.

[[folder:Live Action TV]]
* Sylar from ''Series/{{Heroes}}''.
* The Borg from ''Franchise/StarTrek''.
* The Krillitane from ''Series/DoctorWho'' absorb traits from species they conquer via DNA absorption.
* According to the ExpandedUniverse, the Shadows from ''Series/BabylonFive'' have shades of this.
* The Replicators of ''Series/StargateSG1'' do this several times through the series. When first encountered, they're just a HiveMind of robotic bugs seeking out technology- dangerous, but not particularly ambitious. Later, they construct several human-form Replicators, which are made of [[GreyGoo nanites]], capable of [[MindRape interfacing with human minds]], much tougher to destroy, and much more forward-thinking. One of the human-forms, Fifth, begins developing human emotions as well, and develops a grudge against Carter and Earth and a desire to conquer the Milky Way. When the good guys attempt to evolve in turn- by developing a WaveMotionGun that destroys Replicators and leaves everything else intact- the Replicators reprogram themselves with an immunity.

[[folder:Tabletop Games]]
* ''TabletopGame/{{Warhammer 40000}}'':
** Evolution is fair part of the [[PlanetOfHats hat]] of the [[HordeOfAlienLocusts Tyranids]]. They evolve very rapidly, but there are special creatures called norn queens in the hive fleets, which (aside from controlling their reproductive processes) analyses the DNA of organisms from a recently consumed planet for useful adaptations to incorporate into the next generation of gruesome gribblies in the fleets production chambers.
** One notable incident is a minor fleet being halted over a Tau world because the Tau were doing exactly the same thing: studying the organisms brought to attack, and changing their loadouts to whatever worked best against it.
** A good part of the Mechanicus believes that all knowledge was once held by mankind, and seeking to discover things on one's own instead of recreating it from STCs is heresy. The Dark Mechanicus are those who've fallen to Chaos and started experimenting, resulting in things like giant demonic centaur tanks with guns for heads.
** Quite possibly the best example is this: In 40K, there is an embodiment of hope, who represents every sentient being's desire for things to change. That embodiment is Tzeentch, the ever-changing Chaos god of mutants, sorcerers, traitors and backstabbers and one of the greatest evils in a galaxy that has no shortage of evil. Ironically, he may also be a good part of the reason why StatusQuoIsGod, up until recently - He is fueled by the process of change as much as the result of it and for all his intricate schemes, all of them are doomed to fail because should one of them suceed, he may well go in a PuffOfLogic.
* The Phyrexians of ''TabletopGame/MagicTheGathering'' are constantly improving upon their [[CannonFodder mechanical fighters]], and they [[HordeOfAlienLocusts recycle the flesh of fallen enemies to create new soldiers]] (called ''newts'').
** You wouldn't even know that the first Phyrexian was a vanilla 0/3.
** New Phyrexia has moved past its original mono-black affinity and now has factions aligned with each of the colors. New Phyrexia now has a wider variety of abilities pertaining to each faction.

[[folder:Video Games]]
* A trademark of the ''Franchise/ResidentEvil'' games is the constantly evolving enemies, probably best reflected by the boss of ''VideoGame/ResidentEvil2'', the G-Mutant, aka Birkin. Every time you defeat him he just evolves into his next form, so you have to "kill" him about a half dozen times in just as many forms.
* Fittingly for a race inspired by the Tyranids, the Zerg in ''VideoGame/{{Starcraft}}'' are constantly enhancing their abilities and expanding their ranks via the DNA of other races.
* ''VideoGame/WarningForever'' has an enemy ship that constantly grows according to how you destroyed it last time. Attacked from behind? It grows more armor on its back. Attacked from the side? Same thing. Hit it from a blind spot? It grows a missile launcher. And it never ends.
* The Bugs in ''VideoGame/BodyHarvest'' invade Earth four times over a hundred-year-period, facing the time-traveling human super soldier Adam Drake five times. In each new time period their forces have mutated to become more developed and stronger than in previous eras despite their failure to harvest enough human DNA.
* The Grigori in ''VideoGame/StarOceanTheLastHope'', they advance evolution in order to create a singularity. One of their targets, the Cardianon, evolved from lizard beasts to a space-faring race in only 200 years, at the cost of being [[JustifiedTrope obligatorily]] AlwaysChaoticEvil because they never developed a full conscience.
* This trope is central to the mythology of the ''VideoGame/{{Overlord}}'' series. As Gnarl tends to point out, "Evil always finds a way."

[[folder:Western Animation]]
* In the ''WesternAnimation/LegionOfSuperHeroes'' cartoon after his apparent death Brainiac takes on a new, seemingly partially organic form and proclaims:
--> Evil does not die. It evolves.
** Too bad for him that the cartoon was cancelled before he could properly show off his new "evolution."
* This principle is stated at the end of the first season of ''WesternAnimation/JackieChanAdventures'', when Uncle explains that destroying one evil will allow a stronger one to come into the world. This may be why [[SealedEvilInACan most evil beings are sealed away]] instead of simply being killed off.
** In addition, nearly every MacGuffin collected by the good guys is lost to the forces of evil, once they are sealed off for good.
* ''WesternAnimation/WolverineAndTheXMen:'' The Sentinels in the BadFuture have apparently come down with a case of jealousy toward their Mutant enemies, and have begun trying to copy their powers. The only examples seen are one Sentinel using telekinesis, and a whole line of Sentinels based on Wolverine, healing factor included.

[[folder:Real Life]]
* [[DigitalPiracyIsEvil Crackers.]] Every time companies come out with new ways to prevent theft, the crackers just try again and get sneakier.
* All serious criminals are like this. Gangs, conmen, forgers, embezzelers, launderers and so on. As the police learn new ways to track, stop and prevent their activities they learn a dozen new tricks.