150 years after Return of the Jedi, the Sith returned.
The Sith under command of the vicious Darth Krayt launched a surprise offensive against the Jedi. Eliminating most of them. After the attack the Sith turned on their new allies, assassinating Emperor Fel and placing Darth Krayt in command of the Empire.
However, Fel survived the assassination attempt and rallied a part of his empire to him. He, along with his Imperial Knights, force users trained to serve Emperor and empire before all others, have pledged to win back the Empire from the evil Sith.
Meanwhile, a small group of soldiers adopted by the Mandalorian Clan Odo strive to make a name for themselves.