Varanus

The varanus is an enormous lizard native to the Rahim Wastes. Weighing in at up to 1000 pounds (with most adults averaging about 800) and stretching up to 16 feet from tip to tip, the varanus is a very powerful beast. Its massive scales act as armor plating for the beast while their brownish sandy color allows them to blend in easily with sand and rocks in their natural habitat. 
This lizard's massive muscles allow it to stand a good 2 feet above the ground, unlike many other lizards which keep their bellies on the ground. This allows it to avoid the jagged rocks of the Gods' Staircase and move a speeds much quicker than the average lizard. It boasts 5 sharp claws on each foot for, a mouth full of daggers, and a bony horn in between its nostrils, all perfectly optimized for killing prey. Clearly, the varanus is an apex predator, and even the crocodiles of the Rahim River can't compete with its dominance in the food chain. That being said, as long as a varanus isn't hungry, it isn't a threat - in fact it has a down right friendly nature, making it easy to domesticate.

Domestication and Use

Both the centaurs and the gnolls of the Rahim Wastes have domesticated the varanus. The centaurs have used them nearly exclusively as guard beasts for their villages, whereas the gnolls treat them as mounts. In both cultures, the varanus has become a staple of society, although most villages are limited to only having one, if they're lucky, because of how much food the varanus eats. Near the Rahim River Basin where food is plentiful, however, a well-to-do village or town can sustain as many as a dozen.
Some Drifters passing through the wastes in their quest to see the entirety of Morgrave and have been known to make a connection with a wild or domesticated varanus. Occasionally these Drifters will bring one home with them. As long as the area is relatively dry, the varanus can thrive - too much moisture can lead to all sorts of disease for the poor lizards. Once some enterprising merchants saw these Drifters with their new "pets", they started heading out into the wastes to procure varanus eggs. Many merchants and adventurers die in the attempt - either to the desert or to a protective mother varanus - but the eggs can fetch a hefty sum among exotic pet collectors and warlords to make the risk worth it to some people.