Nano-technology - Not Sufficiently Advanced, as per the Arthur C. Clarke gold standard of sufficiently advanced technology.
The proper names and descriptions of a sword’s parts.
While we’re talking about the subject of constructing religions, I’d like to bring up the concept of the Creed. The creed is nothing more than a simple statement of the religion’s beliefs, meant to be recited. If you cannot write a creed for your monotheistic religion, it probably needs work on internal consistency. Creed examples:
A powerful wizard that the PCs encounter is completely silent. He does not speak and cannot be heard as he moves. Even his spells are silent, but his magic is just as potent.
He has a tendency to summon invisible chairs, place foes in invisible boxes of force, and other "mime tricks".