Only thieves could be matruds.
Matruds could be found anywhere in Zakhara. Those inhabiting the deserts were typically horse thieves. Most matruds were transients, moving from place to place hoping to find work that would also let them steal.
Matruds usually only owned what they could carry on their back.
These individuals were outcasts, and their plight was obvious to nearly all who interacted with them. While in the desert, other individuals often looked down at them. This did not happen as much when they were within urban settings.