Lana Beniko is a human Sith Lord of the reconstituted Empire, born on Dromund Kaas, who begins as an adviser to the Dark Council member Darth Arkous and ends as one of the most prominent recurring characters in Star Wars: The Old Republic. She is voiced by Lydia Leonard; her original concept art is by Chris Anderson.
The competent Sith
Her introduction is an investigation. Beniko notices that her own superior is behaving strangely, digs, and discovers Arkous is a traitor working for the Order of Revan — then goes outside her chain of command to prove it, teaming up with the Republic agent Theron Shan, a Wookiee smuggler and assorted others. That is the character in one move: a Sith whose first instinct is to check the evidence.
Why that matters
Star Wars has written a great many Sith who are powerful and a great many who are treacherous. Beniko is neither, particularly. She is patient, analytical and loyal, which reads as almost transgressive inside an order built on betrayal, and the game gets a lot of mileage out of asking whether she is a good Sith or simply not much of one.
Where to find her
She first appears in the 2013 Rise of the Hutt Cartel content and comes to the foreground in the 2014 Forged Alliances storyline, after which she is present in nearly every subsequent expansion — mission control for four flashpoints, a companion from Knights of the Fallen Empire onward, and one half of the Beniko–Shan partnership that carries the late game.