A Sith apprentice was a Force-sensitive individual trained by a Sith Master to use the dark side of the Force. The age at which a Sith apprentice began their training varied. Darth Maul became apprenticed to Darth Sidious while still a child. Darth Tyranus and Darth Vader, both former members of the Jedi Order, became Sidious’ apprentice, in turn, as adults. Although Darth Bane‘s Rule of Two mandated that only two Sith could exist at any given time, Tyranus broke with the system by training his own apprentices (albeit at different times)—Asajj Ventress, Savage Opress, and Quinlan Vos—while still apprenticed to Sidious.

Sith Masters demanded absolute loyalty from their apprentices, but would betray and replace them if they felt stronger potential in another. Younger apprentices made ideal candidates for masters to turn to the dark side of the Force, as they lacked the emotional control of a fully fledged Jedi Knight. Inexperienced youth were easier to taint and twist to the purposes of the Sith.