The world of Sansoli has been without sunlight for just over two centuries. The new continual night and a war with the Night Clans devastated the Human populations until The Church and the Vampires came to a truce and eventual peace accord. The the Humans and Vampires came to live together in the various cities left over and all were under the governance The Church. The elite Royal Houses of the Vampires went underground, loosing their names and doing their best to blend in with the rest of the Vampire population as the merging of communities took place.
Of course, part of the reason for peace was that the Vampires realized that without the Humans, things would go very, very badly for them. Even if the other Night Clans disagreed with them both diplomatically and violently.
The former Royal Houses, quietly, covertly, establish The Société. A group of Vampires working in secret to discover the source and reason for Sansoli's lack of a sun.