Holy crap these guys are huge.
Not really big but they can surprise you since they're buried under the sand. Once you hit one they spring up and typically scare the crap out of you.
They remind me of an enemy from Final Fantasy X. They were small plants in the sand but when you walked up to them they'd pop out and fight you.
These things aren't involved in any quest content, which is kind of a shame given how cool they are. The Dune Worms seem to be there purely as a Dune reference, don't know about these guys.
They don't drop anything of note of course.
Este PNJ se puede encontrar en Tanaris (39).