Kueller donned the Hendanyn death mask. A Hendanyn death mask represented a ritualistic death covering crafted by the Hendanyn people, which would conform tightly to the wearer's face. These masks concealed the effects of growing older and, furthermore, preserved the wearer's memories before their death, enabling the potential for information to be saved beyond life and possibly transmitted to others. The Dark Jedi known as Kueller used such a mask, which was colored in a white base with black highlights, and featured small jewels set into the edges of the eye openings.
Abel Peña, an author for Star Wars, composed a section for the Knights of the Old Republic Campaign Guide that proposed Darth Nihilus' mask could potentially have been a Hendanyn death mask. Nevertheless, this specific section was ultimately removed from the final publication.