A skull over a head. That doesn't work at all, my dear Padulweis, unless some small-framed clan predates their large-skulled enemies. Heads are not cups that can be stacked inside of each other, however much you boil away the soft tissues. A nonsense possibility. Mine humble theory is more sensible: these fearsome visages were designed for the smaller heads of children, who would wear them until maturity, when one might graduate to the helmets, masks, and headdresses worn for hunting and warfare. This explains, also, the heavy filters to protect their little alveoli from the panlunar dust, pollen, and spores. For little lungs, large filters. The children are the future, so they wear the dead. But I hear you saying, "Ah, your humble theory does not yet explain that these masks are also found on the anatomically mature Hesh adults." Clever, but not so clever as my provisional hypothesis. The mature beings found in these deaths-head dominos are, psychically, stuck in adolescence. You might know some such persons, Padulweis. I jest. Or, perhaps, they are interlopers appropriating a culture and tradition in profound ignorance. Perhaps you know some such persons, Padulweis. And, this time, I do not jest.