The Diclonius are a newly evolved species, arising from and very similar to average Humans, but possessing psychokinetic abilities far beyond any Human. For reasons that may be cultural as well as biological, they are often at odds with Humans to the point of threatening to replace them as Earth's dominant sentient species.
While Lucy was indeed the first and 'Queen' Diclonius, in fact, her late mother was the source of the mutation that birthed the virus in her children. Lucy's birth fulfilled the messianic expectations of the well-heeled and highly positioned Kakuzawa clan, a number of whose family members possessed a genetic mutation that gave them vestigial horns. Despite this, their cult-like beliefs, and the literally world-shaking steps taken on behalf of Diclonius supremacy by Chief Kakuzawa, the two groups were unrelated. Sadly, the treatment of the Kakuzawas in feudal Japan and their reaction to it would foreshadow the relations of Humans with the true Diclonii, centuries later. Chief Kakuzawa also believed that the Diclonius were the Oni (Demons within Japanese Mythology) that were meant to surpass and replace Humans when their messiah was born.
Anatomy and Physiology
The differences are both outwardly visible and internal. Their heads have bony protrusions that resemble cat ears, but are in fact a mix of bone and cartilage, possibly the result of an extremely enlarged pineal gland in their frontal lobes. These vectors have the ability to manipulate objects and are precise enough to have cutting power, and can be very destructive when unleashed. They are perhaps telekinetic in nature, and can seemingly break bonds at the molecular level.
Diclonii have the ability to detect one another, such as when Kurama released Nana from the offshore laboratory to search for and retrieve Lucy. Even this ability had limits, as she could not sense her target when she was in her childlike Nyu persona, nor could she sense the Mariko clones (Alicia, Barbara, Cynthia, and Diana) when they were under the control restraints set up by Nousou and the Agent riding herd on them during their assault on Maple House.
Diclonius all heal very quickly and do not scar easily. Diclonius are extremely intelligent, however they are just as emotional as Humans, often more so. Once pushed to the brink, some hear a voice that claims to be the directing voice of their own DNA, urging them to kill as many Humans as possible.
Diclonii all have similar hair color and eye color in the anime (shades of purple and pink), but in the manga they have different colored hair and eyes. The reason for the same colored hair and eyes in the anime was to tell Diclonius apart from regular Humans, since the anime was so short that it needed to be easily defined from the very beginning.
In the manga, it is mentioned that Diclonii might fall into a coma if they lose one of their horns, and would never return from their lethargic state if they lose both horns. Lucy's horns grow back though and manage to recover from this twice, at least once becoming more like devil's horns than cat ears. Their vectors usually have a limited range of a few meters. Lucy's are able to extend to two meters, and while Nana, Mariko, and her clones are shown to have either more vectors or greater normal range, her raw power is such that it came to threaten the world. However, the use of such levels of power, ultimately turned to healing Kouta's mortal wounds, lowered and then finally destroyed her own body's integrity.
There are two main classes of Diclonii. One is Lucy, the Queen, the others being Silpelits. The Silpelit Diclonius variety cannot reproduce, but instead use their vectors to infect Humans, turning their children into Silpelits when they are born. Other types include the many clones of Mariko, who was arguably the most powerful Diclonius and a boy born of Chief Kakuzawa's rape of Lucy's mother, the true source of Diclonius DNA and the vector-born virus, despite being fully Human. The Kakuzawa family had, for many generations, believed that they were Diclonii as well, and built up a world-shaking scheme based on promoting Diclonius supremacy, including detonating a missile laden with the virus in the skies over Japan. Though this belief turned out to be mistaken, the threat from the Diclonii kept on even after the deaths of Lucy and Chief Kakuzawa, with the cycle of attacks and retribution ensuring no possibility of co-existence between the races. It is revealed in the final chapter that a temporary world-wide birth ban coupled with the use of the Anti-Diclonius Birth Vaccine helped lead to the end of this threat, though not before the death of at least a notable portion of the world's population. The war's duration seemed to be less than five years, since ten years after Lucy's death, Kouta is seen in the company of his roughly eight-year-old daughter, meaning at least the birth ban was definitely lifted, indicating near if not total elimination of the threat.
It is said by some in-story that the Diclonii were chosen by God as the new Humanity, born with the instinct to destroy the Human race and repopulate the world. In the final episode of the anime, Lucy tells Kouta that *I was born to kill Humans*. She seems at times to have yet another separate personality born entirely of the DNA-driven Diclonius instinct to kill Humans, which may or may not have been responsible for her killing his family, a thought rejected by Kouta himself as an excuse. However, Nana's character, as well as the incidents surrounding Lucy’s past and relations with Kouta, suggests that it is possible for Diclonii to have empathy towards Humans, and that their sadistic characteristics develop as a result of their interactions with the world. Barbara, a clone of Mariko claimed to have also heard this voice. But her personality was shaped by birth and life in a lab, and seemed to have all of Mariko's sadistic tendencies without any of her tempering characteristics. Nana once seemed to have heard it, but was in shock from leaving Kurama and was taunted by Bando as to her lack of a place in the world.
It may be said that the homicidal tendencies are a result of an unstable psyche, itself a result of congenital recessive mutations, aggravated to such high levels by inhumane treatment from Humans. Through the run of the series, the question is raised to the audience (but not answered) of whether the Diclonius homicidal tendencies are an inborn drive to eradicate Humans, or if (just like any "normal" Human child) they developed this drive in response to years of physical and psychological abuse. The homicidal behavior observed in Diclonii has only ever been directed towards normal Humans; towards non-sapient animals (which do not pose a threat to them) Diclonii can behave quite affectionately. This is exemplified in the anime when a young Diclonius girl is shown killing a Human for laughing at her, but when the Human's dog attacks the Diclonius and bites her hand, she does not think to harm the dog but reacts in shock and begins to cry uncontrollably (however, that was an example seen shown as Professor Kakuzawa described their homicidal tendencies, no non-sapient animals actually attack the Diclonii in-series).
Diclonii tend to be heavily discriminated against (infants are often euthanized on the spot) by other Humans, and the series makes it unclear whether the often murderous hostility Diclonii show as well is innate or the result of the hatred and contempt shown against them.
Researchers at both the Kakuzawa facility and the government-controlled facility believed the Diclonii to be a serious threat to the Human race. Diclonii are for the most part kept in isolation and fed by tubes. When Kurama's daughter, Mariko, is born as a Diclonius, he remembered an incident in which an escaped Silpelit touched him with her vectors. At this point, he realized that this explained his daughter's condition and an explosion of such births, with Diclonii passing on their DNA and causing Human parents to have horned children, in theory up to the point that normal Humans would be displaced as the planet's dominant species. Lucy mentions the danger to the Human race to Kouta in the final episode: *Given just five years, I can ensure that there are more babies of our kind born in the world than there are normal Humans.* It is strongly implied that the two good personas in Kaede have been reincarnated into these young girls. If one counts Lucy and Nyu as separate from Kaede, then perhaps even little Nyuu herself is part of this rebirth.
- Silpelit #35 "Mariko"
- Silpelit #3
- Silpelit #28
- Silpelit #7 "Nana"
- The only known Male Diclonius, who was the son of Chief Kakuzawa and also Lucy's half-brother
- The many clones of Mariko , aka #35