From Labyrinthe Wiki
Factions represent player lead power blocks that have grown over the years with the growth of the world background and are tied to a specific character. Whilst the direct benefits of these factions are quite weak compared to say the basic tier of a guild the PC heads of those factions and other members may well provide a more help in getting started from their own personal resources. The main strength behind a Faction is that they have an established background and offer a great variety of roleplay hooks and opportunities for new characters who want something a little different to the usual guilds.
Only Organisations that grant in game benefits are listed as Factions and you will need to consult the relevant Almanac for a list of the benefits granted by these factions and, as per Noble Houses, you require the specific permission of the Faction's leader before being able to start up such a character or be signed into that Faction.