Umbara, known as the "Shadow World" due to the lack of sunlight on its surface, was a planet located within the Expansion Region. Resting within the occluding Ghost Nebula, Umbara was cut off from the rest of the galaxy. This resulted in the development of advanced technologies that far exceeded the galactic standard by the native Umbarans, though it was difficult for non-Umbarans to use the technology. Among these breakthroughs were a gas that stimulated soldiers to fight longer and harder. During the initial stages of the Clone Wars, Umbara was a member of the Galactic Republic, though it would defect to the Confederacy of Independent Systems following the assassination of senator Mee Deechi, who had represented the planet within the Galactic Senate. In response, the Grand Army of the Republic would launch a successful invasion of the Shadow People's homeworld.
During this invasion, Anakin Skywalker was called back to Coruscant at Chancellor Palpatine's request. Jedi General Pong Krell took over the 501st in Anakin's absence. After Krell betrayed the 501st Legion by telling them that the soldiers of the 212th Attack Battalion were actually Umbarans disguised as clone troopers. Rex realized Krell was working for the Separatists. Dogma, feeling betrayed, killed Krell while they were in custody of the Clones, and was himself taken into custody.
- Jedi of the Republic—Mace Windu, Part II (Mentioned only)
- Catalyst: A Rogue One Novel (Mentioned only)
- Star Wars: The Clone Wars – "Darkness on Umbara" (First appearance)
- Star Wars: The Clone Wars – "The General"
- Star Wars: The Clone Wars – "Plan of Dissent"
- Star Wars: The Clone Wars – "Carnage of Krell"
- Star Wars: The Clone Wars – "The Gathering" (Appears in flashback(s))
- Star Wars: The Clone Wars – "An Old Friend" (Appears in flashback(s))
- Leia, Princess of Alderaan (Mentioned only)
- Star Wars: The Force Awakens Beginner Game
- (First identified as Shadow World)
- Ultimate Star Wars
- Star Wars: Absolutely Everything You Need to Know
- Star Wars: The Force Awakens: The Visual Dictionary
- Star Wars Character Encyclopedia: Updated and Expanded
- Star Wars: Aliens of the Galaxy (Indirect mention only)
- Star Wars Propaganda: A History of Persuasive Art in the Galaxy
- Star Wars: Absolutely Everything You Need to Know, Updated and Expanded
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