Darth Nathemus was a male Human who, during his life, was a Jedi Knight of the Old Jedi Order, a Dark Jedi of Darth Revan's Sith Empire and the reigning Dark Lord of the Sith. Born as Aryn Kallo on the Galactic Republic's capital world of Coruscant, Kallo was taken for training by the Jedi at a very young age and at some point became the Padawan of Jedi Master Tarla Denarys, studying under her until her death, at which point his training was taken over by Vandar Tokare. In later years, he passed the Jedi Trials and not long after became one of the many Jedi to go to war against the Mandalorian Neo-Crusaders.