The Valsharess is the drow matron who threatens to invade Waterdeep at the start of the Hordes of the Underdark campaign. She has amassed an army of drow and other denizens of the Underdark through force and diplomacy, and she retains an elite squadron of assassins called the Red Sisters. Little is known about the Valsharess personally other than her ambition and determination. Even her name is unknown, as "valsharess" is merely a title – meaning "empress" in the drow tongue – that she has given herself.
After the hero rescues Halaster from the drow in Undermountain, Halaster places a magical geas on the player, forcing him/her to do his bidding and kill the Valsharess. The hero's hunt for her culminates after the drow invasion of Lith My'Athar. Upon her army being pursued to her keep, the Valsharess commands the archdevil Mephistopheles, whom she had earlier bound to her service, to teleport the hero into her courtroom, where she traps the hero within a magical barrier and then orders Mephistopheles to kill him/her. Mephistopheles, in turn, defies her order, killing the Red Sisters in the chamber instead and releasing the hero from his/her prison, allowing him/her to kill the Valsharess.