it is usually the DM's job to remind players on key things that their character know but they don't. a DC 5 or 10 religion check upon seeing shadowheart's circlet or armor followed by a brief resume of shar upon success feels appropriate, the same way we can get information about intellect devourers, the descent or what a soul coin is (it's definitely not a crypto currency).
I'm not halfway into reading this thread, but I wanted to not forget to +1 this really, really well-made point
