[hilariously it is what good old ortus has told him, on truth juice that neither of them realized, though even there he says,] Why should I bother to answer that when you skirt around every question I've asked?

Even without what I know some things are obvious enough. 'Sacred mystery' is just another way to say God's dirty secret. And if it needs constant guard either it is actively sought or you fear whatever is inside it getting out.