Anakin Skywalker once traveled to Ilum with his mentor Obi-Wan Kenobi, so that Anakin could learn to build his first lightsaber. When Obi-Wan wasn't looking, Anakin started playing with his BB gun, but then a stray shot ricocheted back in his face and broke his glasses... so Anakin concocted a story about a lightsaber crystal falling from the cave ceiling and hitting him. Obi-Wan didn't buy his story and chopped Anakin's BB gun in half. Other Jedi who trained on Ilum: Barriss Offee, Ferus Olin, and Bruce Wayne.
It is believed that Kyle Katarn built his Fortress of Solitude on Ilum to escape the stress and torment of the mortal world. Ilum may also have been the base of operations for a Sith cult called the "Iluminati."