Darth Duisternis

"Today the downfall of the Empire begins! The false monarch that rules you is in truth a rogue Sith, a slaughterer of masters, a weakling whose Empire shall be crushed at the hands of the true Sith!"

 was an ancient Sith entity and founder of the Great Sith Realm of unknown species. He was once a powerful Sith during the days of the ancient Sith Empire. He used extremely rare and powerful Dark Side Force magics to preserve his life in a deep hibernative state after the fall of the Sith, where he went into hiding on the Sith homeworld Korriban during this millenia-long period known as Lord Duisternis' Dark Hibernation or simply the Dark Hibernation. When the powerful former Jedi Aden Aventus came to Korriban in response to a Force calling, Duisternis was awoken from his slumber. Using various manipulation tactics, he turned the former Jedi Master to the Dark Side, knighting him as Darth Infernus. They then formed the Great Sith Realm, a new nation encompassing Korriban and several other Outer Rim planets, declaring war on the Galactic Empire and the Alliance to Restore the Republic in what would be known as the Imperial Sith War or the 300 Day War. He would eventually be destroyed at the hands of his former Apprentice, Darth Infernus, who overcame his darkness and defeated the ancient Sith, soon after ending the War and destroying the Realm.