An extremely arid planet with less than twenty percent of its
surface covered in water is considered a Class H: Desert world.
While many of these worlds are very hot and covered in a blanket
of glittering sand, these conditions are not requisite for a desert
classification. In fact, a desert world may be both cold and rocky.
Though precipitation is rare and the climate harsh,
drought-resistant plants and animals are actually quite common on
desert worlds, and many support humanoid populations.