Trade in the City of Erezzi has long been dominated by two rival consortiums: La Mace d’Ars (the Crimson Mace) and L’Orzi Verci (the Ebony Ring). But the two are forever at each others throats. In 1282 membership of such an organisation was made illegal and both went underground. Now with a quasi-mafioso presence they pervade the city’s businesses, providing security for their members, but causing sectarian tensions between communities.
Start the characters off separately as they arrive in Erezzi, trying to make a living for themselves, buying a shop and setting up a business. Then get them enrolled in one of the two organisations (it would prove most interesting if they ended up in different organisations: think of the intra-party tensions that would ensue!).
The characters could be sent off to disrupt meetings of the other consortium and kill the leaders, they could be captured and tortured and have to escape, but eventually they’re going to meet up with one another, and realise that maybe things would work so much better if they all cooperated. Or maybe they’d see it as an ideal opportunity to get back at each other.
In the end, they could be captured by the authorities and banished for membership of an illegal consortium. Then they’d have to survive in the wilderness outside the city of Erezzi and try to forget their earlier enmities…