Diclonius

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.

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.

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.

Diclonii also have the peculiarity of having the same color of the eyes and hair, even when reddish or purplish pink,

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) 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. 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 is entirely possible that the Diclonius species was actually very normal and/or peaceful, and that the voice of hatred they have is only caused by the prejudice being put against them.

Diclonii tend to be heavily discriminated against (infants are often euthanized on the spot) by other humans, and it is 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