The Sith were Force users who, unlike the Jedi, used their abilities and powers for their own selfish needs and purposes. They were regarded as a cruel and scheming people, resorting to almost any means to achieve their goals (be it ruling a cult or harnessing an ancient energy) and even killing innocent lives just to do so. Most Sith were obsessed with the idea of immortality and great power. As their were not restricted by a code, the Sith were not afraid to learn and utilize new techniques. Their main source of power comes from their anger and rage, acting on these feelings to enhance their abilities.