- "The mountainous ice planet Ilum is home to one of the Jedi Order’s most distant outposts. Nestled between snow-covered crags is an enclave used by the Jedi for generations, a shelter from the cold and a launching point for journeys into Ilum’s exotic crystal caves. These caves produce some of the most rare and powerful lightsaber crystals in the galaxy. Ilum hosts no indigenous population, although a number of larger animals survive in its environment. Its temperatures fail to reach the extremes of Hoth, but it has never been a target for colonization or occupation."
- ―In-game Codex (Planets)
Ilum is the ice planet home to many of the Adegan crystals used in the construction of Jedi lightsabers. The Sith Empire launched an assault on Ilum during the Cold War. The Republic and the Jedi both were unable to launch an effort to retake the planet, and resistance against the Empire on Ilum remains minimal.
Originally, it was thought that the Sith invaded Ilum to deny the Jedi of their lightsaber crystals; however, recent evidence has surfaced suggesting the Empire is using the crystals as a power source for a dark and terrifying new weapon that may tip the balance in favor of the Sith. During the years of the Treaty of Coruscant, Ilum became one of the biggest battlefields ever known.
Ilum missions are offered as a bonus after completing main class quests. The minimum level to start the missions is 47. All missions and enemies are level 50.
- "Before the war, what’s now the largest space traffic hub on Ilum was only a barren field of snow, ice and crystal. With the Empire’s return, Ilum became less of a remote temple world for Jedi pilgrims and more of a Jedi holdfast against the encroaching invaders. Ilum’s unknown location and hard-to-navigate hyperspace lanes made it ideal for hiding important assets and launching sneak attacks, though its primary value was in providing lightsaber crystals for the suddenly militarized Jedi. As Ilum’s military value increased, so did the size of its landing zones. Now that the Empire has come to Ilum, the landing zone has become a fortified complex of considerable dimensions and a vital target for Imperial attacks."
- ―In-game Codex