The Dragon's Tail
Hobgolins tend to be the bread and butter bureaucracy of the empire from what can be seen. Mostly, the people in charge of imperial government such as tax collectors and slave colony satraps.
Goblins seem to be the grunt labor, and the majority of the slave handlers.
Worgs work in tandem with goblins, and seem to occupy a level just above them. The goblins have to handle more of the tedium of slavery, but a worg will ultimately be punished for letting slaves escape.
The player races are all submitted to slavery unless they somehow came from a group outside the empire. Only one currently matches this definition, and he is rarely with the group.
Creatures of all sort inside the MMs still survive in the Dragon’s Tail until I say otherwise.