Ilum / Legends Ilum was an ice planet in the Unknown Regions , one of the main sources of the valuable Adegan crystal s used in the construction of Jedi lightsabers . The caverns containing the crystals were long ago turned into a Jedi temple . Unlike the crystals of other planets , the crystals of Ilum were limited to blue and green in color . The planet was over ninety percent ice . History . Discovery by the Jedi Order . The Gree had established an enclave on Ilum and used it as a launching point for the exploration vessel " Gray Secant " to conduct a multi - century exploration mission . Ilum was first discovered by the wider galaxy in 22 , 800 BBY when a Jedi , navigating hyperspace in the Force , felt a strong pull from deep in the Unknown Regions . Following the sensation , the scout determined that the Force ' s call was strongest on the system ' s fifth planet . Reporting back to the Jedi High Council on her findings , the subsequent research teams detected no signs of previous inhabitants on the barren world , aside from local flora and fauna that had evolved to survive in the harsh environment . The real wealth of Ilum was not discovered until one survey crew was chased into a mountainous ravine by local predators and discovered the mother lode of kyber crystals just beneath the surface . Made up largely of the rare kathracite , pontite and mephite crystals , the trove was an invaluable source for the crystals needed to power a Jedi ' s lightsaber . When the High Council learned of this discovery , they dispatched artisans , scholars , and other Jedi to protect the caves and research how deep they went . Instead of reporting the discovery to the Galactic Senate per custom , the High Council deleted all records of Ilum from their ships and removed mention of it from all reports . A team of surveyors within the Order mapped out a complex route through hyperspace from Metellos that would take a Jedi team directly to Ilum . In order to navigate the course however , one would need the prowess in the Force that only a fully trained Master would possess . With the planet protected , the Jedi built temples and enclaves over the years and the world became a destination of pilgrimage for Jedi intending to construct new lightsabers and Jedi Masters seeking a quiet place for intense meditation . Over the greatest source of crystals , the High Council commissioned the construction of a grand Temple . Upon completion , the Temple over the Crystal Caves began to host the Gathering , a formal part of a Padawan ' s teaching during which they embarked on a pilgrimage to Ilum to search for a lightsaber crystal and build their first weapon . After several millennia of hosting the Gathering , Ilum became the Order ' s primary source for the rare crystals . Some time before the Cold War , the Sith Empire attacked the planet with a force of Sith and shock troopers , killing the Jedi present there . Although the Jedi Order was devastated by the loss of Ilum , the Galactic Republic lacked the resources for a counter - attack . Intelligence suggested that the Sith operations on the world could have extended beyond the harvest of lightsaber crystal s and , due to the amount of local Sith investments , Republic leaders and members of the High Council suspected that Ilum may have possessed a far more valuable resource . One of the resources turned out to be a use for the crystals to power a cloaking device for spaceships , or even a whole space station . Darth Malgus , taking advantage of the chaos in the Empire following the defeat of the Sith Emperor , rallied a primarily non - Human army and tried to establish a base in the system . Malgus ' s attempt was thwarted , and the cloaked armada never saw further use . A return of the " Gray Secant " saw both Republic and Imperial forces striving to gain influence with the Gree and learn the ship ' s secrets , but Ilum itself remained a contested world for the remainder of the Galactic War . Eventually , the Order reclaimed Ilum and once again hid its location , removing records of the battles there , which only lived on as dark legends of the past . Despite the planet ' s overall importance , the High Council recalled all members of the Order that were living on the planet , back to Coruscant and shuttered all facilities save the primary Temple . With no one to maintain them , most of the other Jedi installations were consumed by the planet ' s constant snowfall or crushed under moving glaciers . Clone Wars . In 22 BBY , Ilum was the location of a Separatist ambush . When Count Dooku , leader of the Confederacy of Independent Systems sent a battalion of droids to the planet , the Crystal Caves were heavily damaged . Jedi Grand Master Yoda aided Jedi Master Luminara Unduli and her Padawan , Barriss Offee , in defending the Crystal Caves from chameleon droid s . For a portion of the war , the Jedi Order decided that it was too dangerous for Jedi Initiate s to travel to Ilum to build their lightsabers , so shipments of lightsaber crystals were delivered to the Jedi Temple on Coruscant . Unduli oversaw one of the shipments aboard the starship " Sedawan " when it was attacked by a group of Nightsisters led by Sai Sircu , who sought to pilfer the crystals to power the " Devastation " , an ion pulse cannon – equipped warship that they were building in conjunction with Dooku and the Confederacy . Around 20 BBY , Yoda and Padawan Ahsoka Tano led a group of promising Jedi Initiates in the ritual known as The Gathering , where they would brave the dangers of the Crystal Cave and find crystals to make their own lightsabers . They used the Force to enter through a cave entrance . Later history . Because its existence was not known generally to non - Jedi , Ilum was virtually forgotten after the destruction of the Jedi and Palpatine ' s information purges . This gave the remaining Jedi a safe harbor . After Order 66 , Obi - Wan Kenobi received intelligence that his friend , Jedi Master Garen Muln , had returned to Ilum to hide in the crystal caves . Ferus Olin , a former Jedi apprentice , returned to the caves to retrieve crystals to build a new lightsaber and he also found Garen . The Jedi Master had grown weak during his time on Ilum . He gave Ferus his old lightsaber , which needed new crystals . Ferus inserted his crystals and carried the weak Jedi Master out of the caves . Obi - Wan came to their rescue before the Imperials could take them hostage . Another Jedi also took refuge there : Fy - Tor - Ana . However , according to Garen , she returned to Coruscant to see if any other Jedi had survived . She did not return , but it was rumored that she was imprisoned on Coruscant . Ilum ' s secrecy was not to last . After scouring the Temple Archives on Coruscant , the Empire swiftly moved in to seize the planet . As part of Order 66 , the 481st Legion was dispatched to the planet to eliminate any hiding Jedi and to secure the Temple . After the Empire was fully established , the 481st was replaced with a dedicated joint forces mission of the Imperial Navy and Army . Forming up a beachhead around the Temple and installing a giant metal door over its entrance , the army constantly monitored the facility while the Navy formed a blockade around the planet . Over time , research facilities and observation platforms were established and an entire garrison was situated there . Despite the Emperor ' s grave concerns for the planet ' s safety , more often than not the posting was used as a punishment or sort of exile for delinquent officers , rival captains , and a graveyard for derelict ships . During the Galactic Civil War , Captain Malthegn oversaw the blockade from the command deck of the " Hoplite " . During the Empire ' s hunt for Moff Kalast , who was leaking information to the Rebels , they discovered a Black Sun base above Ilum . Boba Fett , in the " Slave I " , disabled their sensors so an Imperial fleet could capture the pirate leader . Behind the scenes . In the " " TV series , purple crystals are seen to fall , even though it is stated to only produce blue and green crystals . Ilum is also a planet for end - game content in " " where players can complete both PvE and PvP daily missions . Two of the game ' s final instances are also located there .