Firmament

The Firmament reigned over the 10,000 Dawns. They broke the Christmas Needle Agreement so Chris Cwej's superiors, who thought of them as an inferior race, sent Chris as an agent to the Dawns to retaliate.

Lady Aesculapius was a Firmament. (PROSE: A Bright White Crack)

Kasterborus believed that Aries ascended to the Firmament. (PROSE: Introduction and links)

Behind the scenes
The Firmament originated from the 10,000 Dawns series (with a reference to it from PROSE: Introduction and links, which predated 10,000 Dawns by years) and also appeared in multiple crossovers the series had with the Doctor Who universe, none of which are currently considered valid sources by this wiki.

Depiction in the crossovers
The First and Final Firmament were the rulers and keepers of the 10,000 Dawns, playing a role equivalent to the Great Houses of N-Space. (NOTVALID: Rachel Survived, White Canvas)

The Firmament became interested in the universe of the Great Houses because of the Book of Books and sent the Arbiter of Eternity and the Arbiter of Knives to obtain it. (NOTVALID: Rachel Survived)

The Firmament were turned to fiction by Auteur and later saved from it by Graelyn Scythes. Representatives of the Firmament attended the Christmas Needle Agreement and argued with ambassadors of the Bookkeepers. (NOTVALID: White Canvas)