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 as an assassin, Savage Opress, and Quinlan Vos—while still apprenticed to Sidious.