Darth Sephirus

Darth Sephirus born Greka Byzantine was a fallen Jedi that became twisted by a rift torn in the fibre of the Force.
A former Jedi Knight, he was found by scouts following a battle where Byzantine's body was ravaged by injuries due to a cataclysmic event that tore a rift in the fibre of the force and left the planet dead. The scouts figured he would soon die and removed him to a nearby Jedi Academy on a neighbouring planet. However, Greka began to show miraculous recoveries that defied the odds. Soon the Jedi within the Academy began to notice that initiates and apprentices were going missing without trace. Eventually it was learned that Byzantine was responsible, the man now feeding on the Life Force of his fellow Jedi in order to sustain his own life. Corrupted and quickly becoming too powerful he soon harboured a lust for power as the dark side slowly took over.
Byzantine was now referred to as Darth Sephirus of the Byzantine Empire, waging a war that devastated the core, many planets were left dead to the force thanks to his ability to consume the Life-Force. Eventually he was fought at the place where he was injured many years before. During the conflict the self-styled Dark Lord was slain and due to the death, the rift that had been opened was finally healed. In the years that passed, the planet began to finally recover as life slowly returned, though the planet was forever tainted by the dark side. 
His fall lived on as a lesson for young Jedi, his story referred to as The Tale of the Living Wound.
= Foot Note =
This NPC is used within a RESOLUTION Plot and is so part of the RSN Universe of Star Wars lore.