It was scarred by tectonic activity, and the surface of the planet ranged in colors from gray to red from the basalt and mantle, respectively. The atmosphere was dense and showed signs of clouds and precipitation. Sebaddon was covered mostly in lava, containing no oceans or large bodies of water.
Around the time of the Cold War, Lema Xandret went into hiding on Sebaddon after the reconstituted Sith Empire took her daughter, Cinzia, from her to begin Sith training. On Sebaddon, Xandret cloned her daughter and created hexes, a type of combat droid that was able to manufacture itself with great expediency, programming the droids to protect Cinzia at all costs.
When the Sith Empire and Galactic Republic discovered the planet and found that the hexes would be able to take over the galaxy at their rate of growth, they allied for a joint attempt to destroy the droids. The mission succeeded when the clone of Cinzia died, leaving the droids without any purpose. The original Cinzia—now Sith apprentice Eldon Ax—took control of the droids and ordered them to kill Darth Chratis before allowing them to destroy themselves. Afterward, the Republic attempted to retrieve some of Sebaddon's rare metals, but due to attacks by the Imperials, their success was limited. The orbit of Sebaddon was later noted to have been knocked off-course, causing it to begin to spiral down toward the black hole.
In 3650 BBY, Sebbadon was classified as part of the Unknown Regions.
- The Essential Reader's Companion