The designation Sith Knight was bestowed upon a former Sith apprentice after they successfully concluded their tutelage under a Sith Master or another Sith Knight.
During the time of the Jedi Civil War, the number of Sith Knights was less than that of the Sith Marauders, which were a variation of the Sith Warrior. Around that same period, a Sith Knight who was under the direct command of Darth Revan provided training to the Sith apprentice known as Darth Voren.
In later times, the term was applied to a group of force users from the Separatist faction who fought during the Clone Wars. These Sith Knights took part in the Hunt for the Decimator, operating under the leadership of the Chiss Dark Acolyte named Sev'rance Tann. Sith Temples served as training grounds for Sith Knights.
Sith Knight also functioned as an alternative name for the rank of Sith Saber within the ranks of the Lost Tribe of Sith. In 41 ABY, once the Sith Meditation Sphere Ship made its arrival on the planet Kesh, every Sith Knight within the tribe gained the knowledge of how to pilot the vessel.
During the initial development phase of the 1999 film Star Wars: Episode I The Phantom Menace, Concept Artist Ed Natividad created some conceptual drawings of a possible "Sith Knight."
Michael Gough provided the voice acting for the Sith Knights in the 2001 video game Star Wars: Galactic Battlegrounds and its 2002 expansion pack.