Saul Karath
Admiral Saul Karath was an Admiral of the Old Republic fleet, who served under Revan and Malak during the Mandalorian Wars.
Saul Karath taught Carth Onasi everything that he knew about being a soldier. Saul had a brilliant mind, leading the republic to many victories against the Mandalorians. When Revan and Malak went into the unknown regions, to " destroy the last remnants of the Mandalorians", Saul went with them.
Shortly after the Jedi Civil war began, Saul talked to Carth about "how the republic was on the losing side, and how he should start thinking about his survival". Unknown to Carth,Saul was trying to recruit Carth into the Sith. Carth refused to betray the republic, and Saul left to join the Sith.
To prove himself a Sith, Saul took an invasion fleet to Telos, Carth's Homeworld, and demanded it's immediate surrender. The planet refused, and Saul went on to devastate its entire surface. Millions died. Carth's wife was on Telos and was killed, and the Sith captured his only son, Dustil.
When Saul staged a clever trap to capture Revan, Carth, Bastila, and their companions, he "interrogated" them willingly. Saul was not interrogating them: He was torturing them for his own delight.
Saul was killed by Carth on the Leviathan's bridge, during Revan's escape. Saul used his last words to tell Carth that his companion is actually Darth Revan.