Originally known as Slave Gems, because the primitive form would disrupt higher function a bit much for them to be useful at anything else. Of course, Evangela has fixed these issues, the Tesayon gems being her classic style, adaptive semi-intelligent magick that acts also as part of her own mind, so it can never betray her.
The gems were first seen in a realm quite far from here, as another Evangela took an eager young woman into her life, under her spell, forever. This is all that is really known.
The gems are reserved for those who have both impressed and enticed Evangela Anikira enough to inviting them into her twisted little family Tesayon, at least a few of whom can be found on Planet Lilith.
The gems, as mentioned elsewhere, form a bond between those who "wear" them. They also infiltrate the entire nervous system, physically and magickally, as they are bonded with an individual. This means attempting to remove one by force is generally deadly. As Evangela designed them, controls them, and has now found so much more of her own will to use as necessary (not to mention simply being Queen of Tesayon); all those who implant one, generally at her seductive suggestion, after that initial insane surge of pleasure will find themselves eager to follow Evangela and Tesayon, and therefore at least indirectly, Beautiful Sunrise as well.