Goblins and Ogres

When you get lost in the Dungeon, don't lose hope. That's how you become a goblin. The oppressive lack of light, the sparse amounts of food and drink in the Depths, spending all your time in a place steeped in magic, and the loss of hope will all ball up together in the mutagenic process that creates a goblin. While there are plenty of physical changes about becoming a goblin, the most important changes are mental. Goblins are all about survival in the Abyss, resulting in something that most people consider an evil being. Egoism and a lack of taboos creates a being that will happily hunt and eat their former fellow humans. As with dwarves and giants, a goblin that grows old enough will eventually become an ogre.
Given that goblins have zero resistance to the mind control that the Noble Houses use, you will often see nobles use large contingents of goblin and ogre slave-soldiers. Of course, there are limits to their use, since any opposing noble can use their own mind control on them.