Force Rage Ghost

Force Rage Ghost was a Sith Force Power. A Sith when he died, could transform himself into a ghost. How he could was by using his rage and hatred to keep his soul alive. A few Sith used this to keep from dying. One was Palpatine, another was Exar Kun, the last was Supreme Prophet Kadaan. The only way to destroy them was by placing them in such a situation, that they would destroy themselves.