darker than black TERMINOLOGY

Evening Primrose (EPR) (イブニングプリムローズ Ibuningu Purimurōzu?)
A powerful organization of Contractors led by Amber, a former MI6 agent codenamed "February". They aim to reveal the existence of Contractors to the general public, and to promote their status as a new race/group of humans. Special rights and privileges for Contractors are also on their list of objectives.
Hell's Gate (地獄門(ヘルズ·ゲート) Heruzu Gēto?)
A mysterious and chaotic area of space that appeared in Tokyo ten years before the start of the series. Its appearance led to the rise of Contractors and Dolls. A massive Gate Wall has been constructed around it to keep civilians—or anyone else, for that matter—from entering. Several countries, including Japan, are cautiously conducting research on the Hell's Gate, exemplified by a top-secret research facility PANDORA built next to the Gate Wall.
Heaven's Gate (天国門(ヘヴンズ·ゲート) Hevunzu Gēto?)
Another chaotic area of space that appeared in South America and disappeared five years before the beginning of the series, along with everything in a 1500 km radius around it. Its exact nature at this point is unknown in the series. Its appearance apparently started a large-scale war, one in which Great Britain and Argentina participated. Amber, Havoc, Hei, and his sister Pai, were involved in the War and were adversely affected by the Heaven's Gate's sudden disappearance. The area where the Gate was previously located has become inaccessible. Interestingly enough, Heaven's Gate and Hell's Gate are located on opposite ends of the globe, and are considered exact opposites of each other.
PANDORA (Physical Alteration Natural Deconstruction Organized Research Agency)
A UN-operated research facility dedicated to studying the phenomena of Hell's Gate. Located on the edge of the Gate within the walls, an international team of scientists examine the properties of the gate via manned and unmanned expeditions within. Paranormal phenomena akin to ghosts are common here, likely due to the lab's close proximity to the Gate. Though run by the UN, it is not impervious to intelligence agencies; both the Syndicate and CIA have infiltrated almost every level of the research center. PANDORA has a heavily armed security force, consisting of armed soldiers possibly of various nationalities and armored vehicles, meant to protect its facilities and personnel.
Contractor (契約者 Keiyakusha?)
Contractors are individuals who have gained supernatural powers due to the appearance of the Hell's and Heaven's Gates. In Kuro no Keiyakusha Gaiden, it is revealed that Contractors are defects that emerge when humans are unable to become Dolls. The existence of Contractors is kept a secret from the general public by most governments around the world, but they are well-known to the higher echelons of society and in the criminal underworld. Contractors possess two other traits that give them a rather sinister reputation: the need to perform remuneration, which is a bizarre, obsessive compulsive "payment" for the use of their powers, and a generally pragmatic, Machiavellian world view. This is described by the Contractors themselves as a lack of emotion in general, but not much evidence exists to verify this claim. Many Contractors exhibit at least some forms of emotion, including love, joy, guilt, and sorrow.
Later in the series it is explicitly revealed that Contractors are capable of experiencing emotions, but that those feelings do not play a prominent role in their thought processes. They are described as being totally rational, and totally amoral. The general rules seems to be that they feel no guilt, and they cannot form or retain social bonds. A normal Contractor cares, in essence, only about their own well-being, and everything is reduced to a cost/benefit analysis: any other issues like laws, emotions, or the question of the sanctity of human life are irrelevant to them.
Doll (ドール Dōru?)
Emotionless "mediums" created to mimic the forms of humans. Dolls can form a variety of functions; the most commonly seen in the series is their use of "observer spirits", which serve as reconnaissance. Dolls have different mediums through which they can send their observer spirits and must be in contact with this medium while observing; for example, Yin's medium is water, through which she can send her observer spirit anywhere else there is water. A Doll can also act as the perfect sleeper agent. It can be given the memories and personality of another person and assume a person's personality perfectly, mimicking all their habits, dreams, and feelings until the time is right. Interestingly enough, a Doll by the name of Shinoda Chiaki seemed to have some "life" of her own by saving Hei from being killed by another Contractor. This suggests that Dolls, like Chiaki, can go beyond their "set" characteristics and become "something else". Other examples include when Huang discovers Yin crying, when Yin hugs Huang when saying goodbye, July expressing confidence in himself and November 11 as a team, July staying with Suo of his own choice, and Sakurai, a Doll stolen by the yakuza, smiling as she runs away with one of the yakuza who fell in love with her.
Moratorium (モラトリアム Moratoriamu?)
An intermediate between a Contractor and a Doll. Moratoria appear to be people with Contractor powers who do not require remuneration as part of their power. Unlike Contractors, they do not have control of their powers, shifting into a hypnotic state of unconsciousness as they use them. Moratoria also suffer from severe mental trauma as a result of their power. According to Mao, the chance of a Moratorium morphing into a Contractor is near-zero, but possible.
Regressor (喪失者 Sōshitsusha?)
A Contractor who loses their powers in exchange for a flicker of hope for a normal life. There are very few known Regressors, and the way one becomes a Regressor is also unknown.


Nick holding the Meteor Fragment.
Meteor Fragment (流星の欠片 Ryūsei no Kakera?)
An object coveted by many intelligence agencies and organizations, and once held at PANDORA. It seems to be connected to the appearance of Hell's Gate; however, PANDORA does not believe that it is of much importance as they had already discovered a similar substance in South America before Heaven's Gate disappeared. Its appearance resembles a large lens, and when inside the Hell's Gate, it displays an as-of-yet unexplained synchrotron light. The Meteor Fragment was first stolen by Nick for the CIA. It was then stolen by Hei who infiltrated the PANDORA installation by orders from the Syndicate. It was then obtained by Amber, who holds it to this day. This object allows entities which do not exist (such as ghosts) to appear, and also allows entities which exist to disappear.
Contract Payment (契約対価 Keiyaku Taika?, also referred to as "Remuneration" or "Obeisance")
True to their names, all Contractors must "pay the price" for using their powers, whether they wish to or not. Moreover, it seems that the amount of payment required is dependent on how much the Contractor uses his/her power. Although this payment can be delayed, especially in the midst of combat, it is ultimately unavoidable. Each Contractor has a unique remuneration, reflecting the chaotic nature of the Hell's Gate. The cost is performing an action, different for each Contractor, ranging from the mundane to the bizarre (some examples include baking, eating cigarettes, or breaking one's own finger). Not all contractors dislike their remuneration, and at least one uses it in conjunction with his own ability.
It is also possible for a Contractor to fully pay off his Contract, but this is an incredibly rare feat, requiring a drastic and traumatic sacrifice. In the series it has only been seen to happen in those Contractors who have the ability to swap bodies, where their contract requires them to eventually lose their original body as remuneration.