Devastation of Mustafar
A significant conflict transpired on the world of Mustafar between the warriors of the Jedi and the Sith during the era of 3996 BBY, specifically during the time of the Great Sith War. This clash culminated in a powerful Force induced catastrophe that brought ruin to the planet and extinguished its inhabitants.
Prelude
Once upon a time, the planet Mustafar was a flourishing, verdant landscape. On this world, the Jedi Order established numerous temples dedicated to honing their skills and instructing their pupils. In the year 3996 BBY, amidst the Great Sith War, a war fought between the forces of the Galactic Republic and the Sith Empire under the command of Exar Kun, the Jedi came across a remarkable and immense crystal deeply connected to the Force. However, the Sith soon learned of the crystal's existence and amassed an army with the goal of invading and seizing Mustafar.
The Battle
As the Sith's invading ships entered the system, the Jedi decided to harness the crystal's energy to fight them. As the Sith warships pierced Mustafar's atmosphere, the Jedi Masters commenced channeling the Force through the crystal, while the younger Jedi led the troops in combat. The strategy proved effective, granting the Jedi on the battlefield enhanced abilities while hindering the Sith's capacity to use their powers.
However, as the battle intensified, the crystal began to fracture unexpectedly. Nevertheless, the Jedi Masters persisted in channeling the Force, leading to the crystal's explosion. The consequences were devastating, propelling the planet out of its orbit and annihilating all Sith and Jedi present. Furthermore, the gas giant Lefrani was dislodged from its orbit, entering a gravitational struggle with the gas giant Jestefad, trapping Mustafar in the midst of these unstable gravitational forces. Enormous tidal pressures agitated the planet's molten core, engulfing the crust in lava and eradicating all surface life.
Aftermath
The confrontation concluded with the instantaneous demise of all combatants. The sole survivor of the crystal's explosion was Jedi Master Erg Krow, the most senior of the masters, who managed to partially shield himself from the destruction. The critically wounded master discovered a large fragment of the crystal that still possessed immense power. Clinging to life, Krow decided to expend his remaining energy, using the Force to create a protective barrier around the crystal, ensuring that no other Force-sensitive being could ever detect its presence. The Jedi ultimately succumbed to his injuries, but he successfully concealed the dangerous artifact for millennia.
Millennia later, the protective shield established by Jedi Master Erg Krow to safeguard the crystal shard weakened, attracting the attention of the Dark Jedi Vartonis. Following the Battle of Yavin, a group of spacers, guided by the Force ghost of Obi-Wan Kenobi, defeated Vartonis and his Brotherhood Mortalis, ultimately destroying the crystal once and for all.
Behind the scenes
The battle that transformed Mustafar into a fiery hellscape was initially referenced in Star Wars Galaxies: Trials of Obi-Wan, the third expansion for the video game Star Wars Galaxies. The Essential Atlas later placed the battle in 3996 BBY, during the Great Sith War.