Sand Wurm

The Sand Wurm is one of the ultimate predators of the Wastes. Not much is known about them, but they seem to have territories in the vastness outside of the cities. Thankfully, knowledge of these territories are known for the areas nearby cities, so avoiding the Wurms is mostly foolproof. However, this does not stop thrill seekers taking their dune riders to said territories in an attempt to outrun the beast.
It is unknown what the maximum size is to the Wurms, but the largest so far has been roughly a mile long with a circumference similar to a high-rise building. It is also unknown how or how often they mate as well as how courting for the species works.

The above is so far the largest known Sand Wurm to be noted.