Legend Lore: "Gemhead guy with scythe hands" / Vastarani

The Vastarani are a cult of the abyss, demons that to some extent follow the teachings of Ioun, but are not considered proper worshippers, they have a grand desire for knowledge, but has somehow managed to remove themselves from most written and mental records of their existence. Few know that they do in fact exist, even among fiends.
They operate on a ranking system, dividing each type of Vastarani Cultist, identified by what kind of gem their heads are encased in:
Diamond Oracle
Emerald Conjurer
Ruby Seer
Topaz Evoker
Amethyst Illusionist
Sapphire Traveler
Quartz Initiate