Beginning as few numbers of large-scale familial clans along with other associated Grimm-folk tribes (including six-arms demon, darkvine plantman, tree-swinging fabric-strip demon, perfume succubus and blackmud demon) who were under their leadership, they became one of the most influential factions behind the establishment of (original) Mistral empire. Besides their own unique associated Grimm-folk tribes types combinations, they had own economical and productive specialties as well, which may had sort of relationship with Grimm-folk tribes, and even some of them had possession of fast-traveling devices, which were given by [certain mysterious provider], including teleportation point system for transportation and commercial purpose.

At first, they usually were responsible for leading and managing their own associated Grimm-folk tribes, and were mainly focus on their own business while rarely intervene the interior affair of Mistral. Later on, their influence began to become more powerful than before, only not overshadowed the political power of Mistral's royal family, but also became ever powerful rival along with Mistral's military force, ever after the establishment of (Second) Mistral empire. Their powerful influence were not just limited to economy aspect, but also extended to military (specially in terms of mercenaries) and political aspects as well. Acknowledging the Grimm-folk's existence in Mistral was considered as the common knowledge and it was not uncommon to spot on these families while a certain familial member surrounded and protected by a number of Grimm-folk tribal members, whose face is full of Grimm-tattoo, as the bodyguards across large crowds of people on the busy street.

After the Great war, the (Second) Mistral empire may not collapsed by the military result against other Remnant world's kingdoms, but rather caused by interior conflicts between ruling-over-Grimm-folks families. These clashes only not caused massive property damages and casualties among commoner's living, but also added the additional ineradicable scars to the (Second) Mistral empire's power, including on political, economical and military aspects, which caused to unavoidable end of (Second) Mistral empire's ruling. In order to able to recover the sincere damages more smoothly, both sides came to the series of agreements to better recover the damages, including hiding the existence of four underworld families and every associated activities along with the existence of Grimm-folk tribes who were under the underworld families' ruling under public eyes, limiting the activities of Grimm-folk tribes on Mistral's surface, and forbidding any contacts with current resident of Kingdom of Mistral as well. The level of secrecy is so great that current resident of Kingdom of Mistral seemly forget the existence of four underworld families and associated Grimm-folk tribes completely, perhaps until the day of revealing.

{Interior structure} In general, inside of each familial clan could roughly be catalogued into three classes: Clan leader and their families at the top, following with abyss general, and lately supporting retainer/attendant at the bottom.

The clan leaders mainly deal with internal and external matters for their own clan, which are including economical and diplomatic ones, along with handling matters related to the Grimm-folk tribes, including leading and overseeing the underworld families' own Grimm-folk tribal members.

Following, the abyss general fulfil both roles of direct operational subordinates toward to their clan leader and overseer to "supporting retainer/attendant", also they are only qualified individual for participating the [Bout of abyss], and while detailed context of choosing the abyss general remain unclear, these method are included being appointed by the clan leader, being enlisted from the "supporting retainer/attendant" or passing throughout the selection trial, furthermore in terms of operational method, they tend to either operate as a whole group, subdivide into several sub-level ranks among their own rank or separate into several smaller groups.

And finally, supporting retainer/attendant 's status are close to the trainee or recruits in military terms, and besides handling daily tasks and other menial matters, including growing food, cleaning the residence and producing commercial goods etc., they also handle small-scale missions like patrol and intel gathering and sometimes accompany and assist the "abyss general" in some of large-scale operations, including combat operation.

As a rule, their hierarchical structure are relatively stricter and heavily enforced on the relations between these classes and also the "other outsiders", such as being forbidden for the "supporting retainer/attendant" to receive gifts from "clan leader and their families", and also being forbidden for the "other outsiders" to have any interaction with "clan leader and their families" without their permissions.

{Western clan} Centered around at western side of Mistral's capital city, the Western clan focus on commercial trading, information gathering, and sometimes hospitality services. Their associated Grimm-folk tribes are mainly assembled by perfume succubus (p.s. high potential of having lots of young girls). Despite being one of the most powerful and influential families in Mistral once, their influence have received subtle downfall due to the escapee of clan leader's own younger heir from their clan, who disappeared without any tracts. Therefore, the clan are currently supported and operated by their own Grimm-folk tribal members.

{Southern clan} Centered around at southern side of Mistral's capital city, the Southern clan's business fields are only just skilled in agriculture, medicine and information gathering, they are also skilled in dust mining and production, especially their utilization of "Dust farming" technique for having vast improvement of dust production that able to rival with Schnee Dust Company, and moreover they not only have certain connections and handle some business with some of upper-class traditional familial clans in Mistral's capital city, but also even have established commercial trading partnership with [Grand Fa-Grim city] in Vale. Their associated Grimm-folk tribes are mainly assembled by darkvine plantman, tree-swinging fabric-strip demon and blackmud demon, and then there are a great amount of [darkvine plantman] and [tree-swinging fabric-strip demon] among their rank of "abyss general". About their relationship with others clan, they have some sort of rivalry with the Western clan, both in business and interpersonal aspect, and keep in their own relative neutual statement toward the Northern and Eastern clans.

{Eastern clan} Centered around at eastern side of Mistral's capital city, the Eastern clan is the most powerful and influential clans among other underworld families. Among the vastly ranges of businesses they handle over, they are not just predominant in handling mercenary business and oversea shipping, they are also highly skilled in weaponry and armed vehicles research and development, anything from small as standard military weaponry to biggest as city-size floating battlecruiser. Having the highest amount of Grimm-folk tribal members, not only have highest quantity of fighting personal among other underworld families, but also have highest economical power and political influence as well, including planning to participate next election of Mistral's capital city's mayor position.

{Northern clan} Centered around at northern side of Mistral's capital city, the Northern clan are famous for the incredible skill in construction and mechanical industries. Their associated Grimm-folk tribes are mainly assembled by six-arms demon with the certain amount of blackmud demon. Because of the relatively chaotic situation of their "clan leader" 's families, they currently are stated by semi-official governmental structure, in otherword their influence are governed by subgroups leaded by "abyss general" individually, which are similar to confederation structure, and so that their Grimm-folk tribes tend to more independent than others and less depended on "supporting retainer/attendant", who mostly join in the subgroups leaded by "abyss general". Due to above mentioned situation of their "clan leader" 's families, their "clan leader" 's families' leadership influence are no longer applied on their associated Grimm-folk tribes, and also there is the rumor said that the de facto leadership of the [Northern clan] have fallen into the hand of [certain Grimm-folk tribal member] actually.

{Bout of abyss} This tournament event was originally used as dispute resolver between the underworld families, and later some of familial clans view it as akin to entertainment/sport event, which was used for emphasized on how powerful and influential these participated families are. The referee role of this event usually are held by clan leader's closest relatives, and even sometimes by [Protectors of boundaries] and Mistral's royal family's members. The context of this event could be ranged from general sport contests like ball games and brawling, to even larger and more serious ones such as massive turf wars and competitive heist events. This event is operated on "winner-first-come, first-served" basis, meaning that the suggestions or opinions made earlier by the winner will be used first, and the losing-ones need to be submitted to the winner's suggestions or opinions.