Go to the firefight lobby. In the background picture, you should see a structure with 2 windmill like (more like circle mill) beams jutting into the sky. Look below them. You should see an elite pointing to a direction, commanding the grunts to go there. He is holding an energy sword in his LEFT hand. Once the picture moves to the right a bit, you'll see another elite on top of the structure, looking at the camera, holding an elite in his left hand.
In the Lone Wolf ending, you see an elite foot in the way of the camera, and then his energy sword, which is held in his left hand.
Thel Vadam used the energy sword in his left hand, if I am not mistaken. Could these be descendants of Thel?