...And not just because she can take on the image of the various Klingon and Terran "Devils".
What is ironic here is that the Klingon home world had not yet been named "Qon'Os" (Pronounced Kronos), Picard has to refer to "Feklar of Klingon"- in the first season, we had heard The Klingon home world referred to as simply "Kling".
Marta DuBois is "Ardra", a "devil" figure for the planet "Ventax II". She literally steals this whole episode.
The enterprise receives an urgent distress call from some scientists on Ventax II, look for another notable performance from character actor Paul Lambert who is in the movies planet of the apes, Spartacus, and all the presidents men. He is the one who implies, when Picard asks, that the danger is coming from Ardra, who is for all intents and purposes, "the devil".
And Marta is a remarkable "Devil", she plays the part with gusto and enthusiasm, as well as some very nice costumes. When she appears in Picard's quarters, she is the epitome of the word "sexy".
And so we have another courtroom drama like we had with "the measure of a man", Picard challenges her claim on Ventax II, which by now includes anything that was in orbit, including the enterprise and everybody in there.
And, it appears that she can enforce her claim, it does not seem like there is anything the enterprise or any member thereof can do to stop her from doing what she wants to do, she can change her form, she can move people around at will, she can cause earthquakes on the planet, and she can even make the enterprise completely vanish. How do you fight somebody with powers like that, is she another member of the Q continuum?
The answer to these questions is hilarious, as Picard ensues a legal fencing match. He initially gets trounced, but Le Forge gives him something to hide "up his sleeve".