Ilum crystals were the most common lightsaber crystals used amongst the Jedi until up to the Great Jedi Purge. Found in crystal caves on the Unknown Regions planet of Ilum, they were similar in structure to the Adegan crystal variants of mephite and pontite, which produced the best lightsaber blades. However, while those crystals were rare even in the Adega system, Ilum presented to the Jedi Order entire caves full of high-quality crystals. Most Jedi Padawans underwent the ritual on construction of their first lightsaber at Ilum.
- Star Wars: Knights of the Old Republic II: The Sith Lords
- Jedi Quest 1
- Jedi Quest: Path to Truth
- Outbound Flight (Mentioned only)
- Star Wars: Clone Wars – "Chapter 15"
- Star Wars: The Clone Wars – "The Gathering"
- Coruscant Nights II: Street of Shadows (Mentioned only)
- Star Wars: The Force Unleashed (video game)
- Knights of the Old Republic II: The Sith Lords: Prima Official Game Guide
- The Complete Star Wars Encyclopedia
- Jedi Academy Training Manual
- Star Wars: Edge of the Empire Core Rulebook
- Star Wars: Force and Destiny Game Master's Kit (Mentioned only)