Kueller is seen wearing the Hendanyn death mask in this image. A Hendanyn death mask refers to a ritualistic death mask crafted by the Hendanyn people, designed to conform perfectly to the wearer's face. This mask served to conceal any indications of aging and, furthermore, possessed the capability to preserve the wearer's memories leading up to their passing. This allowed for the potential continuation or transference of knowledge beyond death. A notable example is the Dark Jedi named Kueller, who donned a mask of this type, distinguished by its white colored base, black detailing, and the presence of small jewels inlaid at the edges of the eye openings.
In the Knights of the Old Republic Campaign Guide, a section penned by Star Wars writer Abel Peña suggested that Darth Nihilus' mask could possibly be a Hendanyn death mask. Nevertheless, this specific text was removed before publication.