The Great Scourge of Malachor, also known as the Battle of Malachor, was a battle between the Jedi Order and the Sith Empire on the planet Malachor. During the battle, the Jedi attacked the Sith temple, a battle station and superweapon capable of destroying life. The remains of the battle, in which combatants were left petrified, remained preserved for thousands of years after the Great Scourge.
The petrified bodies of Jedi and Sith were left on Malachor.
By 3966 BBY, Darth Tanis created the superweapon on top of the Sith temple. Millennia before the Cold War, the Jedi Knights attacked the forces of a Sith witch and the Sith temple on the planet Malachor. In the ensuing battle, the temple was activated, resulting in the death of everyone on the planet. The petrified bodies of the combatants were all that remained, left littered across the battlefield. The battle also involved other archaic superweapons that were fueled by dark side energies. The horrors of Malachor would go on to inform Jedi legends for millennia to come, and stories of the battle were interpreted as tales or forewarnings for Jedi younglings.
While training Darth Maul, Darth Sidious brought Maul to the site of the battle to teach him about the fall of the Sith. Sidious forced Maul to breathe in the ashes of his Sith predecessors. While breathing the ashes, Maul proceeded to have visions of the deaths of thousands of Sith warriors at the hands of the Jedi.
In 3 BBY, the petrified remains of the battlefield were discovered by Padawan Ezra Bridger, Jedi Knight Kanan Jarrus, and the former Jedi Ahsoka Tano. Tano, remembering her Jedi teachings, recalled that a battle had been fought on Malachor. Bridger wondered if the Jedi had won, but Tano deduced from the remains of the battlefield, that nobody won. Bridger found a green-bladed crossguard lightsaber, which he briefly activated before it shorted out. After Jarrus was blinded by Maul, he found a Jedi Temple Guard mask and wore it while briefly dueling with Maul on the side of the Sith temple.
The Great Scourge of Malachor was first referenced in the 2015 reference book Star Wars: The Force Awakens: The Visual Dictionary, which stated that the crossguard design of Kylo Ren's lightsaber was an ancient one that dated back thousands of years to the Great Scourge of Malachor. The book's author, Lucasfilm Story Group creative executive Pablo Hidalgo, added the reference to the book to connect it with the battle that was ultimately referenced in "Twilight of the Apprentice," the second season finale of the animated television series Star Wars Rebels.
Although the exact events of the Great Scourge have yet to be revealed, Star Wars Rebels executive producer Dave Filoni shared his thinking for what the battle was. In his mind, the battle was fought when Jedi Knights attacked the Sith temple that was being constructed by a Sith Lord, the voice of whom became the Presence in the obelisk that is activated by the Sith holocron that Ezra finds in "Twilight of the Apprentice." In this idea, the temple either fired or misfired and led to the petrified destruction that remained on the battlefield for thousands of years.