It's a... Magic... thing. I only know some of the details, but the darker the Jewel, the more powerful you are, so if someone has a lighter Jewel than yours, you can smash them into a bloody pulp in a fight. Or at the very least intimidate them.

[Molly isn't preening that his Jewel is clearly darker than Caleb's at any rate. Caleb has him beat on knowing practical uses for magic, while Molly is just a finesse weapon cutting at threads without considering what made them.] There's also a lot of politics involved in it, but I stay out of that. I'm just trying to keep things going smoothly here so I don't waste my afterlife in another war.