What animal manages to survive in a sweltering desert with mosnters roaming the land? Surprisingly, the Horned Lizard. Not only does it survive, but somehow, after a few generations, it becames a predator. And a nasty one at that.
Roughly the size of a dog, these little menaces are not to be underestimated. They can burrow into the sand, hiding with just their ugly heads sticking out. Their powerful legs push them through the sand, maintainign this camoflauge, and when they reach their favorite prey, usually a nice tasty horse, they spring out, clamping their powerful jaws into the nearest prey, before dragging them off into the distance.
Sand Stalkers, while ordinarily solitary creatures, have been known to work together. Like the sharks of old, they have an amazing sense of smell, as well as the ability to spit blood from their eyes. When they find a large group of horses or food, they will spit blood from their eyes at the targets, marking them. And then it's as simple as drawing moths to a flame.
They don't want you. Just your horse. And once a Sand Stalker bites you, it is not letting go, even if you kill it. So do yourself a favor, if it comes down to you or your horse, get the fuck off. Sure, not easy surviving without the horse, but a hell of a lot easier than surviving with no leg. Try telling that to the nomads though, stubborn bastards...
Mud. Water, while a very valuable thing to have in the desert, is a good way to slow down a Sand Stalker. A lot harder to move through mud than sand for the Sand Stalker.
Cold. Sand Stalkers are cold blooded, a nice blast of cold wind, or anything that can cool them off will send them packing.
Aim for the neck. A Sand Stalker's Dewlap, more commonly known as the weird neck flap thingy, is more than just a way to look big or attract mates. It's actually a collection of veins, arteries, and nerves. They can extend this Dewlap to catch the sun, warming the blood in their systems, as well as retracting it to help keep from getting too hot. This is also a rather soft part of an otherwise armored little beastie. Cut it, spill lots of blood, and eliminate one of the critters main survival techniques. Won't save your horse, but it'll rid the world of a Sand Stalker, and that's always a good thing.