Quote Originally Posted by Ramza00 View Post
The mechanics of a "title" which we do not understand, nor do we understand its meaning.
My guess:
Spoiler: Princesses
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A princess is someone who draws on Etheria's magical energy instinctively, with relatively idiosyncratic results. The runestones are First Ones tech, which help draw in those magical energies and directs most of them to a connected princess, while transferring some portion to the Heart of Etheria. The power boost to the princesses is how the First Ones convinced a few of them, long ago, to participate in the setting up of the runestone system.

I'm basing this mostly on the time when Razz tells Mara that Etheria, and not the sword, chose her to be She-Ra. This suggests that Etheria can produce a She-Ra without the sword, and I'm extrapolating from there to the other runestones.