The sand itself probably acts as an anchor, depending on how far down the legs go. Considering all the bits and bobs and giant hairs sticking out of them, they seem be intended to generate a good deal of friction.



I imagine it would walk by moving one leg at a time, to maximize the friction they generate. I can also imagine it letting off more gas than usual in the event of strong wind, both to increase its weight and sink into the sand more.