Deep Rule

The Deep Rule, usually referred to as just "The Deep". They mostly operate in the larger towns and cities, but might have a contact or two in smaller villages that lend themselves to smuggling. They control more "questionable" activities (gambling, prostitution, smuggling, assassinations, etc.).
They are usually thinly tolerated by the authorities as long as they keep their members mostly under control and don't cause problems for the wealthier class, but occasionally they'll "not keep their place" and the authorities will feel the need to make an example of them.
This usually happens after The Deep has stolen from, killed, or otherwise annoyed someone who is high enough up the chain that they can't be ignored.
The two centers of power are Bayport and D'Hara, with the island split along the mountains that run through the center of the island (got a name for those yet?) These centers have final say over all of The Deep's activities in the smaller towns and cities of territory, but generally don't get involved the day-to-day business occurring outside of the two large cities unless they feel something is happening that will affect the overall organization. The leader of these respective centers is referred to as "The First" (short for "The First Rule"), i.e. "The First of Bayport". These two leaders tend to cooperate with each other, but neither trusts the other and are generally quick to react to anything that seems like an incursion into their respective turf.