Hexenaltar

Hexenaltar(ヘクセナルタル; Hekusenarutaru, german for Witches' altar) is an indepentent organization of Magicians from European roots which main objective is to archive and report the history of Magic, its evolution and development and research of all forms of magical knowledge around the world.

A neutral human force of magicians in  Highschool DxD: Яe-birth which swore to never directly be involved in the affairs of other factions, the character Tasha Campbell is a member of this organization by studying Fire magic, Leech magic and magic from hell.

Summary
"Guardians of the history of magic, neither good or evil, indifferent to the World. For them, knowledge triumphs over darkness or light."

- Tasha Campbell Hexenaltar is a mysterious, obscure magical association composed by several families of magicians and wizards with the sole objective to research, date and finally archive all forms of magic, either old or new, into their original country, a moving, flying library that cannot be reached by normal means, and only the current head of said country is able to freely go in and out, other magicians, even those of higher status, having to be permitted into such. Since they vowed to only serve as 'observers' of events and document the history and progress of magicraft instead of taking part of it, little is known about their origins or members, said to date from even the dawn of mankind.

The Bookmen
Magicians of the clan, known as Bookmen(lit. Historians of Magic), are taught since early age the art of witchcraft and magical gathering and once their training is complete, their are allowed to enter Flying Library and be given the title as a full-fleshed Bookman, with now the permission to explore the world around them under the condition that they must, in any shape or form, gather some form of knowledge regarding  magic. Although the organization itself is neutral and indifferent to the world, members of the Hexenaltar with the exception of its head have permission to fully engage and even take part of affairs from other factions, as long as they follow a certain number of rules such as not reveal the position of  other Bookmen if not under strict circunstances or contact the Flying Library or Hexenaltar itself and ask for it to meddle in third-party conflicts. Moreover, while magicians might serve their whole lives in order to research a single magical subject, they're also allowed to explore other branches of knowledge thanks to their special form of spell known as Leech Magic(リーチの魔法; Rīchi no mahō), which allows them to absorb any form of teaching faster, as seen when Tasha was able to easily grasp the basics of Touki from Liu Bei. Members are also allowed to engage in battle in order to see if the kind of magic they're working on is worth it of their time, although they rather not, with the exception of the Campbell.

When a Bookmen dies, a magical seal in their brains processes all forms of knowledge into ink, and back at the Flying Library, a book under their name and magic will start wiriting down all forms of knowledge and equations they have gathered over their years, not to mention their own history and familiar roots. It is the job of the Head Magician of it to then read the books, separate the worth of the unworth and then finally put the former into a sphere of light on the heart of the library, known as the Grimoire(グリモア; Gurimoa). As for now, the reason for such is unknown.

The Flying Library
The Flying Library(飛行図書館; Hikō toshokan) is the main Headquarter of Hexenaltar, an enormous, country-sized flying land that guards the main lobby with a dense forest and under a powerful spell that makes it unreachable and invisible even for other factions, being inhabited only by the Head of the organization in order to separate the new information of other Bookmen. The vast land has at its heart the main Library, where an immense number of books are archive and protected by the Head, all of them left blank with a single dry quill for each next to them linked to a Bookmen's brain and life. Once a bookmen dies and their minds are processed and written down, said book falls to the ground in order to be picked and analized by the Head in order to separate their informaton.

It is unknown if anyone but the head inhabited the Flying Library.

Members
It is unknown the real number of members or families affiliated with the Hexenaltar since they are not much inclined to claim their position of such and they tend to forge several alliances and partake into several other organizations throughtout their lives, although it is known that certain clans do maintain a tradition to become Bookmen to serve as a legacy, such as the Campbell. The only members that have been fully associated with it are Tasha Campbell, the Bishop in Berolina Gremory's Peerage and the current Head of the Flying Library, Siciliano Ford.

Trivia

 * The organization and their members are based on the Bookmen Clan from D. Gray Man.
 * The name of the Organization is a reference to one of the two rock formations at the Summit in Brocken, the highest peak at the Harz mountain and said to be home of Witches and demons, such as seen in the tale Faust.
 * Bookmen are known to lend their children by the age around 7-8 in order to become one of them, it is even Hinted that Magicians adopt lost orphans in order to higher the number of Bookmen in the world.