The Ground Ones inhabit a massive area centered in the Southern Plains but extending from the Dry Ocean to the edge of the North Country. Their population is innumerable, divided into discrete (to them) kingdoms. No one knows the exact nature of their underground kingdoms, but they have the ability to house their entire population and store food, arms and supplies. They have an absolute monarch, and place a high value on self-sacrifice for the monarchy.
The Ground Ones are experts in group warfare and hiding their numbers. Often it is better to pay a small tribute when passing through their territory rather than risk being overrun.