Pure Parin, the only metal left after the God Fall (a cataclysm that among other things tainted all magic) that can still be enchanted with out corruption.

I'm Buddhist, so I'm answering this question from my real-life standpoint:

Authentic Realization of one's Ultimate ( original awareness ) Nature.

What could be more precious?

Given that ALL of one's unconscious-mind's mechanisms exist to block that from happening, to protect unconsciousness's Eternal unbroken dominion, what could be more difficult to earn/obtain?

All the distractions in the world, "helping" one to NOT earn one's deepest profoundest Truth...

All the profits that cease, should one get anywhere in self-realization...

You simply don't need any external resource, for there to be a most-precious-resource, you know?

I was just about to post a question asking for suggestions for something I could use like this for my world, and of course I find this question from a week ago lol.

I might post it anyway just to revive the conversation in other, similar communities. It's a useful MacGuffin.