Plume Coteries

The Plume Coteries, also known as the Bookkeepers, were a faction of posthuman librarians. (PROSE: A Farewell to R.M.S.) Their library was "one of several places that claim[ed] to be the biggest library in the Universe". (PROSE: White Canvas)

History
The Plume Coteries were originally a miniscule posthuman peoples who were known to travel on the backs of majestic birds, (PROSE: A Farewell to R.M.S.) the birdhemoths. (PROSE: Sonnenblumen)

The Coteries colonised the Revelatory Majesty Sphere in the Amazolian system. (PROSE: A Farewell to Arms) The Coteries donated RMS to Roger's family as part of a peace treaty after accidentally desolating the Rogers' homeworld. (PROSE: A Farewell to Arms, A Farewell to R.M.S.)

After discovering the Library, they became predominately known as the "Bookkeepers", but were still interchangeably called "Plume Coteries". (PROSE: A Farewell to Arms, et al.) Most Bookkeepers became closer in size to classical humans. (PROSE: A Farewell to R.M.S.) Some of the Bookkeepers' smaller members acted as dignitaries to the outside universe, using specially-sized diplomatic craft to travel through space. (PROSE: A Farewell to Arms)

When the Great Houses tried to buy RMS from Roger, the Bookkeepers stepped in to help negotiations, postponing the deal for many years due to their lack of field agents. In the interim, they used their books to learn much about the agreements the Houses were making with other powers in preparation for the War in Heaven. When the time came, the Bookkeepers traded RMS in return for the Houses' secrets of time scooping. (PROSE: A Farewell to R.M.S.)

Sometime after this, dignitaries of the Coteries from the "distant reaches of dead space" came to Terra Primagenia to attend the unveiling of Cernunnos. (PROSE: Cobweb and Ivory)

When the painted warriors attacked the 10,000 Dawns, they stole every copy of The Book of the Enemy therein to cover their tracks. However, the Emissary advised Graelyn Scythes, Archimedes Von Ahnerabe and Lady Aesculapius that a copy could still be found in the Plume Coteries' Library. Travelling there via crystalline incision portal, they happened upon Coloth, who was working for the Coteries but not technically a member. The boy got Marissa to consult the catalogue, and Marissa gave them a glowing library card which would direct them to the book despite the place's unthinkable size, but advised Coloth to go with them because the book itself might prove dangerous. After locating it, the group discovered that the painted warriors were servants of the Original Mammoths and travelled via another portal to the alter-time realm the mammoths called home in the context of the war. (PROSE: White Canvas)

Behind the scenes
Sam Maleski's story Thesis / Antithesis / Synthesis in the charity publication Master Works is formatted as a document in the Plume Coteries collection. The story opens with a note that it is a transcript of a voice recording of, which was gifted to the Coteries in 2754 by "Mr. Leonard Dahl".