Mustafar was a small planet controlled by the Galactic Empire. Located in the Mustafar system of the Outer Rim Territories, it was known as a fiery volcanic world where lava was mined like a precious natural resource.
Mustafar was a very young and volatile world, torn apart by opposing gravitational forces of the gas giants Jestefad and Lefrani, with the former being the closer of the two. Astride thick-skinned lava fleas, the natives leapt across the lava fields to mine the planet's deadly natural resources. Mustafarians oversaw the smelting facilities constructed by the Separatists on Mustafar.
Rising of the Empire
Shortly after the founding of the Empire, Obi-Wan Kenobi faced his former padawan, Anakin Skywalker, on the planet. The two battled following Skywalker's assassination of the leaders of the Confederacy of Independent Systems, effectively ending the Clone Wars. Skywalker was critically injured during the duel, and was taken back to Coruscant to be rebuilt as Darth Vader.
Mustafar later came under the control of the Empire after Emperor Palpatine ended the Clone Wars and brought the Empire in to power, resulting the falling of the Jedi Order and the Republic. Afterwards, Mustafar became infamous for being the place where Jedi went to die.
- Mustafar bears a striking resemblance to Io, the fifth moon that orbits Jupiter. Like Mustafar, Io too experiences extreme volcanic activity on the surface. The obvious difference between Mustafar and Io is that Io's volcanic flows are made up of sulfur, whereas Mustafar's are made up of molten silicate rock and iron ore, which are much hotter than molten sulfur.
- Kanan and Hera calling Mustafar a place "where Jedi go to die" is a clear reference to Revenge of The Sith when Anakin Skywalker truly died and Darth Vader was born in his place. It has additional significance, as Rogue One: A Star Wars Story revealed, as the home of Darth Vader's private palace. Pablo Hidalgo revealed that the palace was present during the events of Season 1 of Star Wars Rebels, and that it was where Kanan was being taken. Whether or not Kanan was aware of either of these facts when describing Mustafar has yet to be clarified.