Margot is the senior partner at Will's firm. She is stoic and outspoken and has a tendency to casually insult her employees.
She later appears when she hires Grace to design the firm (requesting a "tasteful bloodbath" theme) where it becomes apparent that she has re-hired Will who is no longer working for the Coalition for Justice. 
- She is married to a man named Leonard, whom she "stopped loving years ago" and even tries to set him up with Grace.
- She frequently has affairs.
- She casually states multiple times that her sister has been murdered. 
- Went to an all-girls school, where she had "half a dozen character-building, lesbian experiences". 
- She outwardly steals from employees, accepting them as "gifts". 
- She is implied to belong to a "secret, evil club downtown". 
Does anyone feel the heat in here? Let's get out of here before clothes start flying off. — introducing Grace to Leonard
Well, you're not going to be partner. And this has nothing to do with those silly studies that say a mother is less productive in the workplace. But there are of those studies, and they all say the same thing. — firing Roz, Partners
Oh, grow up, Gary. Will's getting promoted because his performance reviews were better. This has nothing to do with your uninteresting wife. — Partners
Hector, I've only got five minutes before I have to get back to the office. I want what I had yesterday. I don't remember what it was, and you weren't working, but I want it anyway. — to a barista, Forbidden Fruit
You remind me so much of my sister. They never found her killer. — to Grace, Forbidden Fruit