Dark Lord Darth Tannen. Ruler of the Sith Rebellion years before Anakin Skywalker was born and was killed by Darth Plagueis and his apprentice and future Galactic Emperor, Palpatine, in the moon of Mygeeto.
He leaded the Sith Rebellion and created an army to defeat Dark Lord Plagueis, his old master and father(who abandoned him when he was a little boy) .
His army was destroyed by the Jedi in Nar Shaddaa, after his death.
Darth Isul was a Self Proclaimed Dark Lord of the Sith after Palpatine's death and was born in Endor, son of a Sith acolyte (who trained him) and his wife and spent his childhood traveling through the galaxy. He returned to Endor and remained there for many years in meditation and witenessed the Rebel victory of Endor. In the next day, because was bored,he went to the Rebel camp. After killing many Rebels and Ewoks, he accidentally Force-pulled a giant tree and was killed in that event.