In short, anyone who chooses to attack a Darkhaven shopkeeper will die brutally. In addition, they may find themselves facing the direct wrath of the gods in hell...
Those caught stealing from these shopkeepers will be incarcerated by the city guards until such time as their release is granted by the gods.
A Darkhaven shopkeeper is any mob inside Darkhaven at which you can type list. If you are given a list of items for sale, or are told to try back later, it is a shopkeeper. This also includes guild shopkeepers and the blacksmith.