Mm. Magic itself isn't limited to those who are clan members, in Klein. In fact, even those who possess very little essence can still learn some magic... to be honest, there are still several things we don't really know about the gemstones.

But what we do know is that they mark the contract holders intended to help the Grand Sorcerer—so, for people like myself who were born with them, it means that the original holder... ah... ceased existing before the contract was fulfilled.