Cthulhu Mythos: Skin Deep [5E]

In Skin Deep, the heroes defend the lands of humanity against the machinations of extra-dimensional doppelgängers known as sand dwellers. The sand dwellers corrupt susceptible mortals, hollowing out their bodies and stealing their skins to take their places. They have infiltrated human governments and militaries and are undermining them, weakening them against the invasion by their warlord-queen, Ravazel the Butcher.

Can the heroes unravel their schemes and help humanity stand fast against this otherworldly menace, or will they too be hollowed out and replaced?