Dark Evolution (暗黒進化 Ankoku shinka or ダーク進化 Dāku shinka; Dub: Dark Digivolution) is a corrupt form of normal evolution that is typically triggered when a Digimon falls under some sort of negative influence. A Dark Evolved Digimon is typically very powerful, but also dangerous, aggressive, and uncontrollable.
A common theme with Dark Evolutions is the influence of emotion, either the Digimon's own or that of a human partner. Intense negative emotions, such as anger, hatred, hubristic recklessness, or despair, are what generally triggers Dark Evolutions. In moments where these emotions are so overwhelmingly powerful, a Digimon may undergo Dark Evolution due to their influence. There are also cases where some external force compels a Digimon to undergo Dark Evolution.
Generally, Digimon who are Dark Evolved are totally uncontrollable and unresponsive to their human partner. They are aggressive and indiscriminately destructive, if not genuinely evil.
It is also common for Angel Type Digimon to have demonic Fallen Angel or Demon Lord Type counterparts that they transform or evolve into when they "fall from Heaven" to the Dark Area, which in some cases is the result of them pursuing some negative emotional compulsion, such as anger, resentment, or self-righteous rebellion, that brings them in defiance of God's will. This resembles the basic idea of Dark Evolution.
The Digimon Reference Book defines these Digimon as being the result of Dark Evolution.
- Wendimon: A Dark Evolution of Lopmon, induced by anger and hatred.
- Devitamamon: Rumored to be a Dark Evolution of Digitamamon.
Certain other sources also present these Digimon as the result of Dark Evolution, although the Digimon Reference Book does not define them as such.
- Skull Greymon (Digimon Adventure, Digimon Adventure 02, Digimon World -next 0rder-, Digimon ReArise)
- Metal Greymon (Virus) (Digimon Adventure 02)
- Andiramon and Cherubimon (Vice) (Digimon Adventure 02: Vol. 1: Digimon Hurricane Landing!!/Vol. 2: Transcendent Evolution!! The Golden Digimentals)
- Megidramon (Digimon Tamers)
- Shine Greymon: Ruin Mode (Digimon Savers)
- Black Gaogamon (Digimon Next)
- Ofanimon: Falldown Mode (Digimon Adventure tri.)
- Mugendramon (Digimon Adventure:)
- Meicrackmon: Vicious Mode (Battle Spirits)
In "Dark Evolution! Skull Greymon", Yagami Taichi is determined to try and make Agumon to evolve into a Perfect Digimon so that they can stand up to Etemon, but he totally neglects what Agumon actually wants and tries to force it to happen. When they are fighting another Greymon under Etemon's control in the Colosseum, Taichi takes advantage of his knowledge of evolution as triggerable by the threat of harm to a Digimon's partner, and tries to bait the enemy Greymon into attacking him. As Gennai later observes, this is "the wrong kind of courage", and this causes Agumon to Dark Evolve into Skull Greymon. Skull Greymon immediately runs wild, does not respond to any of Taichi's attempts to communicate with him, and easily overpowers all the Digimon who try to stop him, but quickly runs out of energy and devolves back into Agumon. Gennai then counsels the group that evolving to Perfect requires raising their Digimon correctly.
The experience of causing Agumon to Dark Evolve traumatizes Taichi, and for a while he is afraid to fight or evolve in case he makes another mistake and causes Agumon to Dark Evolve again. In "The Fairy! Piccolomon", Piccolomon puts Taichi and Agumon on a training course that, after an illusory encounter with a younger Taichi, restores their confidence that they can evolve correctly.
In "The Evil Ring's Magic Runs Wild" the Digimon Kaiser abducts Agumon, enslaves him with an Evil Ring, and attempts to forcefully Dark Evolve him into Metal Greymon. At first, his experiments fail, and Agumon evolves into Skull Greymon. The Kaiser is unable to control Skull Greymon at all; when he first deploys Agumon to fight the Chosen Children, Skull Greymon runs wild until it runs out of energy and devolves.
In "The Enemy is Metal Greymon", after further failed laboratory attempts to create Metal Greymon that just result in Skull Greymon again, the Digimon Kaiser concludes that Evil Rings are not powerful enough to process all the data needed to control Perfect Digimon. He then develops the Evil Spirals to overcome this and other shortcomings with the Evil Rings, uses one on Agumon, and successfully Dark Evolves him into a virus Metal Greymon. This time, not only is the Kaiser able to control Metal Greymon, but Agumon stays in the Metal Greymon form indefinitely. He does not devolve until V-mon (as Lighdramon) frees him from the Evil Spiral in "Blue Lightning, Lighdramon".
Digimon Adventure 02: Vol. 1: Digimon Hurricane Landing!!/Vol. 2: Transcendent Evolution!! The Golden Digimentals
After being separated from Wallace and Gummymon, Chocomon Dark Evolves into Wendimon out of loneliness and sorrow at losing Wallace, and desperation to see him again and to "go back" to the way things were.[N 1] Because of this, Yagami Hikari is able to sense its presence as a "crying Digimon" (泣いているデジモン). His anger and despair when Wallace refuses to go with him causes him to Dark Evolve again into Andiramon, and then again into Cherubimon when the Chosen Children's Digimon corner him. Dark Evolving gives Chocomon increasingly potent dark powers, including the ability to abduct Chosen Children and confine them to a dimension within itself, and to reverse aging.
In "The Kindhearted Hero, Leomon Dies!", Matsuda Takato is absolutely consumed by rage and a thirst for vengeance against Impmon (as Beelzebumon), after Beelzebumon kills Leomon. His anger and orders to make Beelzebumon pay force Guilmon to evolve into Megalo Growmon and attack Beelzebumon in a mad frenzy, culminating in Takato ordering him to evolve even further than he ever had before into an Ultimate Digimon. In response, Culumon's powers are triggered (causing him great pain and dread) to Dark Evolve Megalo Growmon into Megidramon. Takato's D-Ark breaks as a result.
When he sees Megidramon, Takato is immediately horrified and regretful of what he has caused Guilmon to become. In "The Name's Dukemon! The True Ultimate Evolution", Megidramon runs wild and engages in a furious fight with Beelzebumon, but Beelzebumon eventually overpowers and defeats it. Megidramon does not devolve for some time until Takato reaches through to him.
Megidramon's abnormal evolution triggers a Digital Hazard so severe that it threatens both the Digital World and the Real World; when Hypnos detects it, they recognize it as the worst that they have ever seen. The Digital Hazard subsides once Beelzebumon knocks Megidramon out.
In "The Day of Parting - The Strongest Enemy: Thoma!", Daimon Masaru is overcome with overwhelming rage at the apparent betrayal of Thoma H. Norstein. He manifests a dark Digisoul that triggers a Dark Evolution in Shine Greymon, transforming him into Shine Greymon: Ruin Mode, a dark version of Shine Greymon: Burst Mode.
In "Destructive Power, Shine Greymon Runs Wild", Shine Greymon is unable to control the Ruin Mode state and goes on a rampage, indiscriminately attacking both Mirage Gaogamon and the city around them. At first, Masaru continues to press the point and demand that Shine Greymon make Thoma pay for everyone that he's betrayed, but Daimon Chika and Bancho Leomon snap him out of it and make him realize what he has done to Shine Greymon, but Shine Greymon does not respond to his cries for him to stop. Bancho Leomon tells him that a Burst Mode running wild cannot be stopped, and that they have no choice but to wait for Shine Greymon to burn himself out. When a tear lands on Masaru's Digivice Burst, Shine Greymon's Ruin Mode state ends and he reverts into a Digitama. Bancho Leomon and Lalamon point out that Agumon may no longer have any memories of his life with Masaru after he hatches, if he ever hatches again at all.
In "Coexistence", the disappearance of Yagami Taichi in JESmon's attack traumatizes and depresses Yagami Hikari, and she begins producing intense dark energy. This energy forces Tailmon (as Nyaromon) to Dark Evolve into Ofanimon: Falldown Mode.[N 2] She then fuses with Raguelmon to become Ordinemon, triggering the beginning of the consumption of the Real World by the Digital World and thus fulfilling Yggdrasill's plan.
Some secondary sources, such as the Battle Spirits card game, also describe Meicoomon's evolutions into Meicrackmon: Vicious Mode as Dark Evolutions. However, Meicoomon's transformations are classified by official Digimon Adventure tri. material as mutation (変異 Hen'i), not Dark Evolution, although they do share the similarity of being caused in part by negative emotion.
In "The Final Stage, Done Devimon", during their battle with Done Devimon, both Yagami Taichi and Agumon are tainted by Miasma. When Done Devimon devours Taichi, Agumon (as Metal Greymon: Alterous Mode) is overcome with dark energy and Dark Evolves into Mugendramon. He attacks Done Devimon in a berseker rage, and Tokomon observes that if he is not stopped, he will become just like Done Devimon. Ultimately, Mugendramon is unable to gain the upper hand and is overpowered. Tokomon saves him by using his powers to snap Agumon out of it and trigger a temporary evolution into his true Ultimate form in order to save Taichi.
One of Gammamon's potential Adult evolutions is the sinister Gulus Gammamon. Unlike other Dark Evolutions in other Digimon anime series, Gulus Gammamon still speaks and does not act berserk. He exhibits a totally different personality that is cold, cruel, fatalistic, and far more "mature" than Gammamon. He outright rejects his Gammamon identity, and he feels absolutely no loyalty or kindness toward Amanokawa Hiro or any of the others. Unlike Gammamon's other forms and the other partner Digimon, whenever one of Gulus Gammamon's attack names attempts to "stream" into Hiro's head for him to command, it causes him great pain and he is unable to discern what that attack name is (because of this, Gulus Gammamon picks and announces his own attacks).
Gulus Gammamon is first seen as an apparition in "The Sewn-lip Man". When Clockmon uses Chrono Breaker on Gammamon to drain his time, it causes an indistinct specter of Gulus Gammamon to appear above Gammamon, scaring Clockmon. The apparition quickly disappears and Gammamon remains in his Gammamon form.
In "Executioner", Sealsdramon's murder of Bokomon triggers Gammamon into undergoing an abnormal evolution into Gulus Gammamon. As Gulus Gammamon, he easily overpowers Sealsdramon, forces it to confess its motives for its killings of Digimon (no motive beyond wanting a high kill count), and then kills it with one Dead End Skewer. He then tries to escape from the group's digital space into the Real World, and when Jellymon and Angoramon try to stop him to prevent him from harming others, he attacks and easily overpowers them and attempts to kill them all with Dark Pales. However, memories of Bokomon's death stop him from hitting them with the attack, and he reverts to Gammamon.
In "The Other Overseer!", Inui Yuu's anger over the death of Trailmon C-89 forces Gaomon to undergo Dark Evolution into Black Gaogamon. As Black Gaogamon, he fights and kills Mummymon and his Commandramon henchmen far more brutally than how he usually fights, before devolving into Wanyamon.
Yagami Taichi's Greymon Dark Evolved into Skull Greymon in Episode 21, "Dark Evolution! Skull Greymon", due to Taichi forcing the evolution by overfeeding Agumon and putting himself in danger. In this form, he destroyed the enemy Greymon sent by Etemon, a part of the Dark Network and a part of the Colosseum with a single Ground Zero. However, Skull Greymon was now running berserk, and was a risk even to Taichi himself, forcing the other Partner Digimon to fight him.
Skull Greymon is the twenty-second obligatory boss of the game, fighting the Chosen Children at the end of Episode 21, "Dark Evolution! Skull Greymon". He can deal damage to one party Digimon with Ground Zero or to all the party with Death Nail. Upon being defeated, he drops the Revive DigiPiece, which allows the equipped Digimon to use the technique of the same name to revive a KO'd ally with full HP.
After the battle, Skull Greymon ran out of energy and devolved to Koromon, who knew he had done horrible things and felt he had disappointed everyone. However, Ishida Yamato reassured him he had done nothing wrong, it was all Taichi's fault. Taichi accepted responsibility and asked for forgiveness, realizing he had felt like he had to fight by himself after obtaining the Crest of Courage.
When Hirose Kouta forces Yukimura to train excessively hard in an attmept to make Yukimura evolve into Mugendramon, Yukimura Dark Evolves into Skull Greymon. He runs wild at this point, forcing Takuto or Shiki to kill him, after which he reverts to a Digitama. The event allows Analogman (while possessing Tsuzuki Shoma) to realize that mutations can bring forth more than just Mugendramon, a knowledge he'd use to create Mutated Super Evolution, turning his partner, Omegamon Zwart Defeat into Omegamon Alter-B.
The Digivice Ver.Complete adds Dark Evolutions as special evolution lines for Agumon and Gabumon. If either Digimon loses two battles in the same stage, their usual Perfect and Ultimate evolutions are replaced with, respectively, Skull Greymon and Black War Greymon, and Were Garurumon (Black) and Metal Garurumon (Black), and they lose the ability to access any other Perfect or Ultimate forms other than these ones. They exit their Dark Evolution lines if they lose two more battles in the same stage.
Dark Evolution is only available once the respective Digimon is unlocked and the Omegamon requirement is unlocked.