The unidentified Sith splinter faction was a small faction that the two Sith Zanisk and Adacin founded circa 3637 BBY. The two Sith fled into hiding in order to avoid fighting against the Eternal Empire and remained hidden even after Empress Acina ascended to the throne to negotiate a ceasefire with Zakuul.
The pair later reemerged on Ord Mantell to establish a small splinter faction that set up their operations in a former separatist base located on the planet. Their idea was to attack those planets that allied with the Eternal Alliance which had risen to prominence at that point during their rebellion against the Eternal Empire. But their activities led to their base being attacked and the Sith and their splinter movement were defeated in the ensuring battle.