Mustafar was a small primordial volcanic planet located in the Mustafar system, situated between two gas giants in the Outer Rim Territories that was aligned with the Galactic Confederacy during the Clone Wars and later taken over by the Galactic Empire.
During the Imperial Era, Mustafar became a fortified Imperial world as it housed the personal sanctum of Darth Vader.
Mustafar was a scorching lava world located in the Outer Rim Territories, and had an array of valuable minerals which were mined by the Old Galactic Republic and later the Galactic Empire.
The planet was situated between the two gas giants Lef'rani and Jeste'fad. The two giants were in a tug-of-gravity with both trying to claim tiny Mustafar as a moon by pulling the planet towards them. Mustafar owes its hellish volcanic landscape and activity to this battle as it causes massive tidal waves that heat the planet's interior. Jestefad's gigantic electromagnetic field swamps Mustafar, generating huge electrical storms on the planet.
While still very hot, the lava on Mustafar was of a lower temperature than that found on other worlds, due to unusual mineral allotropes that were molten at lower temperatures. The storms caused by Jestefad made landing on Mustafar extremely difficult as it interfered with navigational equipment.
As no oxygen existed on the planet, large, stable Oxygen Vents were built by the Galactic Empire on mass and implanted by Imperial garrisons in 17 BBY. By 4 BBY, Mustafar was covered with breathable oxygen.
In 20 BBY, after Jedi Knight Anakin Skywalker had turned to the Dark Side of the Force, becoming the new Sith Lord Darth Vader, he traveled to Mustafar to assassinate the ruling council of the Galactic Confederacy.