Following the commencement of the Clone Wars, a conflict pitting the Galactic Republic against the Separatist Alliance, Jedi Master Luminara Unduli and her Padawan, Barriss Offee, were caught in a surprise attack. This ambush, orchestrated by the Separatists, took place at the Jedi Temple located on the planet of Ilum. Approximately four months into the war, Unduli temporarily ceded command of her army to escort Offee to Ilum for a meditation exercise, intended to aid in the construction of Offee's last lightsaber. During this training, chameleon droids belonging to the Separatists launched an assault, nearly destroying the Temple and trapping Unduli and Offee beneath debris.
Grand Master Yoda subsequently rescued Offee and Unduli. In the aftermath of this ambush, Offee increasingly undertook independent missions, sometimes collaborating with her master.

The initial reference to the Ilum ambush within the current Star Wars canon appeared in "Mace Windu and Other Users of the Force," a publication from Altaya's Star Wars Encyclopedia.
Within Star Wars Legends continuity, the Ambush on Ilum was portrayed across the fourteenth, fifteenth, and sixteenth segments of the Star Wars: Clone Wars micro-series.
- " Mace Windu and Other Users of the Force " — Star Wars Encyclopedia (First mentioned)
- " Exegol, the Unknown Regions and Wild Space " — Star Wars Encyclopedia