A Jedi is a member of the Jedi Order, who studied, served and used the mystical energies of the Force; usually, the light side of the Force. The weapon of the Jedi is the lightsaber, a weapon with a blade made of pure energy. The Jedi fought for peace and justice in the Galactic Republic, usually against their mortal enemies, the Sith and Dark Jedi, who studied the dark side of the Force. Although the Order was almost destroyed three times, including once by the Sith Empire of Darth Revan, and another 4,000 years after that, by the Great Jedi Purge of Darth Sidious, the Order lived on due in large part to the efforts of Luke Skywalker, who forged a New Jedi Order to defend first the New Republic, and later its successor, the Galactic Federation of Free Alliances.