The clandestine religious sects of the Greco-Roman world are often referred to as 'mysteries.' I like how this rings over any discussion of these groups — how the presence of a mystery reminds us not just of the secret business going on, but also the circumstantial, rumor-like nature of any historical gaze, of the divine amongst mortals, unknowing in our midst. (I also like that it leads to moments like 'Mithraic mysteries,' a series of sounds not often heard in my experience of English.)
Of course, such Mysteries aren't unique to the Greco-Roman world. And much of the secrecy within and surrounding these groups stems less from desire for gradeur and clever branding & is more a matter of safety. On a grand scale, safety in the secret might mean greater control of the dissemination and trajectories of a Mystery's own stories, rites and traditions. But secrecy as a means of protection also has a great deal to do with the very literal and immediate physical and social bodies of a Mystery's practitioners, devotees.
In one mystery, Orphism, the fragility and ephemerality of our mortal form held central importance, power and consequence. The body, to Orphic worshippers, is the vessel bearing our immortal-selfstuff-soul through a cycle of reincarnation, a cycle marked by suffering & tragic in its very existence. Among what scholars think are a handful of foundational myths for the Orphic and related mysteries there is a particular tale that describes the jealous Titans (who inevitably end up slaughtering the central/worshipped figure of Orpheus-Dionysus, tearing him always limb from limb and sparing his heart) as disguising themselves in gypsum.
Gypsum is, in fact, a particularly soft mineral — rating about a 2.0 on the Mohs hardness scale (the one where diamonds are a 10 and talc is a 1). I did not know, until I looked at the Wikipedia and mindat entries for gypsum, that it is also the stuff of alabaster and plaster dust. And fertilizer. The rich man's perlite.
How well the Orphics understood the softness of that which separates our hearts from this world.
How they understood fragility and richness.