These are groups that are not signatories to the Treaty. Opportunities to be involved with them may arise in play. You don’t find them. They find you. The Refs may also have DPC roles available for these groups. A DPC is a “Directed PC”. You will be given certain instructions and backstory details by the Refs.
The Arrangement started out as a deal between three gangs in the Hegemony capital of Cranford, where they agreed to stay off each other’s turf and collaborate in their efforts to avoid or subvert the law. The Arrangement’s people often claim that followers of Builder and Aspirant were involved in this plan, in an attempt to give it a veneer of legitimacy. They’re almost certainly right. However it started, the Arrangement adopted a “Join or Be Conquered” strategy that was a crooked reflection of the Hegemony it soon expanded across. Now, “officers” of the Arrangement keep a guiding hand on illicit activities across the Continent, and see a fine chance to get what people want, what they… need, into or out of Mat Sellah. One way or the other. They have been implicated in kidnappings of Faction agents, smuggling and other major crimes on Mat Sellah.
One of the earliest Guilds. Since then they fell on hard times, all the top people sold out to demons or got shanked by the demon cultists. They have been supplanted by the Guild of Physicans as the legitimate trade union, and the Barber-Surgeons are now wholly a demon cult known for their ruthless ambition and widespread network of bribery and corruption. They see the lost treasures of Mat Sellah as power to be fed to their demonic masters, and its scattered villages as a convenient source of sacrificial victims nobody could possibly miss.