Whistler was Human, although it is not entirely certain whether he was a colonist from a world in the Unknown Regions, or perhaps a clone. By the time of the liberation of Kariek, he had been a stormtrooper in Aurek Company of the 501st Legion for six years, the last two of which he had spent in command of the four-man squad designated Unit Aurek-Seven.
In the course of their attempt to breach the defenses of the Warlord's fortress, Whistler and Aurek-Seven encountered a group of native Eickarie freedom-fighters, including the warrior named Su-mil. After Su-mil proved instrumental in securing the capture of the fortress and the overthrow of the Warlord, Whistler invited him to join the Imperial military, and when he left the military soon after, the Eickarie replaced him as Aurek-Seven's leader.