The Nepherides were students and members of a dark side school based on Byss. They were trained, Force-sensitive assassins of the Galactic Empire. They would often wear a plait, and their teeth were carved to look like fangs. Some of those fangs were empty and contained poison capsules, which made their bites lethal.
Specialized in Force drain and using the Force to mask their own presence, Nepherides would often hunt Jedi to absorb their energy.
The members of this school cultivated a strong assiduity to the Byss Imperial court, with the hope to be integrated in the Emperor's Royal Guard.
Behind the scenes
The Nepherides were created by Patrick Bousquet and Christophe Debien for an ambiguously canon roleplaying Gamemaster help which appeared in the French magazine Casus Belli 90. The only illustration was provided by Eric Puech.
Sources
"Dark Sides" — Casus Belli 90 (First mentioned)