Darth Mercurial was a prestigious female Dathomiri Nightsister who was a Sith Lord of the One Sith. Best known as the protégé of Darth Maladi, Mercurial possessed a caustically powerful command over the Dark Side of the Force, and was a highly promising candidate to Darth Krayt as one of his Hands. Although finally passed over for the title of Hand, Mercurial would lead a cadre of Sith Assassins, known by the moniker of "Special Operations Task Force 184", which would be highly successful in eradicating Jedi and Imperial Knights.