The Rani was another renegade time lord from back in Classic Who. Sadly, she was only in two episodes, one of which was with Seven (who I have difficulties with), but her Six episode was made of *win*.

She was on earth covertly murdering people to extract a chemical from their brains that she needed for a research project she had going on, and then the Master showed up. And she was all, "Oh god, *you*? Go away."

And he was all, "The Doctor is here too."

And she, "Bugger. Well, I'll move to some other planet to finish this; there's humans all over the place."

And he, "No! We must destroy the Doctor! And you must help me!"

And she, "Nuts to that. I'm not getting in the middle of your weird little hate!fest/romance thing. I can just be evil *somewhere else*. 'S a big universe."

And then the Master held her experiments hostage till she helped him, but still. Cold-blooded, ruthless, full of herself genius. I adored her.

And if River Song is the Rani, not only is she magically less annoying but she *also* makes sense. Which she does not otherwise do.