Xezbeth

Once upon a time, Xezbeth was a very important demon lord in Hell.   Thousands of years ago she was a leading factor in raining terror down on humanity.  But she was betrayed!  Some 50 years ago an up-and-coming lieutenant in her army saw their chance.  They reported a long contentous enemy of mine making an appearance, that they thought they were unnoticed.  And she was foolish.  As the ruler of lies, she had an innate sense for the truth, and she could not sense any falsehood.  She thought she could finish them off on their own, but they were prepared!  It was true.  They did originally think they were unnoticed, until the lieutenant went down to make a deal.  Xezbeth was unprepared to face such a power, and was struck down.  Weakened, but still with some remaining power, she crawled into the nearest vessel she could find, to recuperate and regain power, a simple sack doll.  She would have gained enough power to retake her position, had she not stumbled across the Witch, who took advantage of her weakened state, and forced her into indefinite servitude.

I mean, that's one of the dozen or so backstories Xezbeth has given on her current situation.  She was a demon of lies.  It's what she does.  All we know is that she works for The Witch, is currently stuck as a sack doll, and is pretty much an asshole.  Also she's a hell of a liar.  She must have retained some of her power despite her predicament, because when she tells you something, you are likely to believe her.  Possibly counters against this ability are knowing contradicting facts to her claims, and just straight up knowing about this ability.  I mean, you can still fall for her lies, but at least you have a chance of going 'waiiiiit a minute'.  She is very good at internet trolling.