Sith apprentice/Legends

Sith Apprentice is a generic title taken by a Sith if he/she is an apprentice. In Darth Bane's New Sith Order, the Sith Apprentice and the Sith Master both held the title Dark Lord of the Sith simultaneously, unlike the earlier tradition of a sole Dark Lord.

This in effect made even the "second" member of Bane's order the "equal" of the great Dark Lords of the past, like Exar Kun and Darth Revan