Shu Yen, a Jedi Master within the ranks of the Jedi Order, served as the guiding figure for the Twi'lek Padawan, Diala Passil. Armed with a lightsaber, he imparted his knowledge of agility to Passil. Considerably prior to 0 ABY, Shu Yen met his end, killed by the Sith Lord Darth Vader upon the moon known as Yavin 4. This event plunged Passil into a state of recurring nightmares, which intensified as time progressed. A lingering aura of darkness and corruption permeated the site of Shu Yen's demise. This evil force reached out to Passil, its influence stretching across the galaxy, relentlessly haunting her thoughts. Upon her return to the location where her master perished, Passil was confronted by an apparition of Shu Yen, who pleaded for her return before morphing into the form of Darth Vader.
The name of Shu Yen was initially alluded to within the news article titled The Veteran and the Exile, featured on Fantasy Flight Games' official website on October 27, 2014. Later, he received direct acknowledgement in the Star Wars: Imperial Assault Core Set, which was launched on December 15, 2014. Within this set, his name is explicitly mentioned on the cards labeled "Temptation" and "Shu Yen's Lightsaber," and also within the Campaign Guide.