at some point following the mandalorian wars, the individuals known as revan and alek squinquargesimus declared themselves sith lords, and became darth revan and darth malak respectively. their brutal campaign against the republic was hugely successful. revan was eventually betrayed by malak, allowing a jedi strike team to capture him. malak continued his conquest without revan's tactical leadership, until a redeemed revan defeated him, and the star forge, the source of the sith fleet was destroyed.