Ilum was a planet in the Unknown Regions.
History
The planet was covered in ice and was the site of an ancient Jedi Temple, dating back to the dawn of the order. The temple housed caves of Kyber crystals. Jedi younglings would make journeys to Ilum to find their own personal Kyber crystal to use in their lightsabers.
Appearances
The Gathering (First appearance)- A Test of Strength (Flashback)