Over time, Hunters have assigned what are known as catalog codes to individual Demon and Fae races. These codes include letters and numbers that determine species, physical type, rarity, and order of catalog and aide Hunters in maintaining criminal records and keeping information classified. Catalog codes are universal and in that sense allow international Hunter bases to communicate information effectively due to races being called different standard names according to country. Catalog codes were created in the English language and so remain consistently English.
In the past, Hunters were required to carry a catalog code book in the case of lesser known catalog codes, but nowadays a catalog code program is included in the standard handheld computer. Catalog codes are assigned and created by a specialized board made up of Hunter researchers from various countries.
Catalog codes contain two letters, a dash, and three numbers, for example DI-110, which is the catalog code for ghosts.
The first letter in a catalog code indicates the species.
F = Fae
D = Demon
H = Human
The second letter in a catalog code indicates the physical type of the race.
H = Human
- These types of races take on standard human forms with some variation in such minor things as eye or hair color. The majority of catalog codes contain this designation.
R = Representative
- These types of races have forms that are representative of human form but cannot pass as humans, such as pixies.
N = Non-human
- These types of races have only one form that is not human or representative of being human.
I = Indistinct
- These types of races typically have no true physical form. This category is limited to only a handful of races, such as ghosts.
C = Changeable
- These types of races are able to change physical shape and may or may not have human forms or the ability to attain human forms.
The first number in a catalog code indicates the rarity of the race ranging from common, uncommon, rare, extremely rare, and paradox. On the actual coding criteria, it is indicated in divisions of hundreds starting at 100 and ending at 500. The rarity number is often considered up to debate as populations fluctuate according to location, which is why the specialized board of researchers in charge of catalog codes is important in maintaining order. Catalog codes do not change unless the specialized board agreees to the change, which is very rare.
100 = Common
- This division is assigned to races that exist practically everywhere humans exist regardless of human ratio. These races are typically encountered on a daily basis and not necessarily for criminal actions. These races also are the races most employed by Hunters, and it is not at all uncommon to see them working in Hunter bases or as part of Hunter teams.
200 = Uncommon
- This division is assigned to races that are usually located in populations with high concentrations of humans. They are sometimes employed by Hunters.
300 = Rare
- This division is assigned to races that the average Hunter will typically only meet once or twice during his or her entire life.
400 = Extremely Rare
- This division is assigned to races that are rarely seen and most Hunters will never directly encounter. This is especially debatable since this may be due to the fact that they are not easily recognizable through physical or magical means and so Hunters do not realize when they actually encounter them.
500 = Paradox
- This division indicates that the catalog code belongs to a group of creatures containing similiar Paradox abilities. This group can be made up of individuals of completely different original races, but due to their Paradox, they are considered a separate sub-species.
The last two numerical digits in a catalog code indicate a specialized number assigned to each race. No two races have the same number. This is to enable that any changes in catalog codes can result with the least amount of changes.