I think there might be two different alliances. One group is good and the other is evil. The group who killed Diageo at the start are a band of thieves and they are in some sort of battle with the nobles. Chairdriver, one of the thieves, is upset that Joey(Joseph Baldwin, Diageo's first character) joined the nobles since they all used to run in a gang of orphans but Diageo got taken in by the nobles.
The thieves can probably disguise themselves and each have a different sneaky power. Diageo could steal, chair could sneakily gather info. I think there are two more of these thieves since I got the impression they were all there on the night Diageo was killed. It appears the nobles are good but they at least have a vigilante.