Sith Lord

A Sith Lord is referred to a member of the Sith Order, who had completed their Sith Training as a student in the Sith Academy.

 Sith Lords In The Shadow Empire 

Nearly another decade of training with a Sith Master or another Sith Lord, a Sith Knight would become the rank of Sith Master. When a Sith Knight becomes as Sith Lord, they can choose to be apart of the Dark Council if there aren't any more spots taken of the twelve seats. The rank of Sith Lord is a great noticeable rank within' the Sith Order, making everyone know that they have considerable knowledge and strength of the Dark Side of the Force.

With the Dark Lord's new rule, breaking the Rule of Two and bringing forth a Dark Council, there can be many Sith Lords at a time. If you're a female Sith Lord, you would get the rank of Sith lady.

With the new uprising of the Shadow Empire and the Sith Order, a Sith Lord or a Sith Lady can become the Dark Lord Of The Sith, but since there could only be one Dark Lord of the Sith at a time, they would have to manage to kill the Dark Lord themselves.