Celebrim
Legend
I don't think you can really system something and then also keep it mysterious.
Early in the current campaign (now almost in its 5th year) I had intended to change the way magic items worked by giving most of them (at least all those worth 2000 g.p. or more in RAW terms) one or more subtle quirks which could only be learned by experimentation. I developed a quite lengthy list of quirks and several of the initial magic items I handed out had such quirks. These quirks included everything from strange cosmetic effects and displays when used, to small alterations in function, bizarre side effects, and even random chances of alteration or replacement of the normal function. What I discovered though is that while the system worked well in theory, once I had 6 players and each began to have multiple magic items it began to be unworkable. It was impossible for me to keep track of, and even if I shared the burden it was clear that it would just lead too much mental overhead. But of course, for a computer all of this strange weirdness would be easily trackable and would I believe serve to keep magic items adequately weird and mysterious.
Likewise, a similar system could be placed in effect for all arcane spellcasting and in a perfect world I could implement both that and my desires regarding layering all locations in a campaign world at a very fine scale with a variety of overlapping auras that influenced spell-casting, so that literally the player had only a vague idea of the full extent of what would happen when a spell was cast and at the least did not know exactly what might happen (good or bad). But such a system again requires too much headspace in play.
I still take pride in my ability to create evocative magic items, but I've been forced to rely on different techniques for doing that.