Naze Valley Rangers
According to legend, derro are somehow related to dwarves, assuming derro exist at all. No one knows exactly how and dwarves hotly dispute the claim, but all agree they are physically lesser than dwarves and somewhat insane.
It has been recently confirmed that derro actually exist, combat having happened in New Crosswalshire or more specifically, under New Crosswalshire. Derro reportedly have the ability to cause darkness in an area and shout out their gibbering madness in a way that causes damage (sonic burst). They also have spellcasters, but exactly what kind is unknown at this time. Their darkness is defeated by the light from a divine casting of continuous flame.
It is currently unknown where the derro under New Crosswalshire came from.