[member="Darth Kentarch"]
Ah I see, although she'll be refined gradually, and Niaana could become that, it would be a long character arc from where she is. She's very much a less stable Sith at the moment, who will play on vampiric emotional tendencies, draining emotional energy that way and using it back on her victims in a sonic form. [member="Darth Ferus"] summed her up brilliantly, as a vaapad weapon returning what she's given. I wish you luck in your search though! It's refreshing actually to have someone lay out exactly what they are looking for!
My other 6 year old (non factioned) Sith Knight [member="Raien Keth"] is significantly closer to that description but still off, as he'd walk over anyone to get to his goal, not out of a desire to kill, simply because he considered whatever was in his way to not be valuable enough to bother noticing. (Blind Pride taken to the extreme)