Antoinetta Marie is a Breton member of the Dark Brotherhood who can be found at the Dark Brotherhood Sanctuary located in Cheydinhal. She wears the basic Dark Brotherhood armor, which cannot be equipped when taken.
Although she seems to be the most "innocent" member of the Sanctuary, her blood thirst is obvious in dialogue. She dreams of taking over Ocheeva's position in the Sanctuary someday.
When asked for advice on "Bad Medicine", Marie reveals that she killed her aunt with poisoned stew and enjoyed the experience, especially when her relative's face planted into her bowl. She was then homeless and claims to be near the brink of death before the Dark Brotherhood saved her. It is also hinted she may have been heavily abused by prison guards. She refers to them as "strong and cruel, so very cruel" if one asks her for advice on the contract "Scheduled For Execution". If asking her this when her disposition is below 30, she will say "I can only hope the prison guards do to you what they did to me. You will know the true definition of the word 'horror.'"
During the quest, the Hero is required to kill Antoinetta, along with all the other members of the Sanctuary.
- Lucien: "I will always think of Lucien Lachance as my savior. When he found me, I was living in a gutter, an inch from death. I owe him everything."
- Night Mother: "I've always wondered who the Night Mother really is. Some say she's an old woman who lives somewhere here in Cyrodiil, but I'm not so sure."
- Sanctuary: "Have you ever lived on the streets, struggled to survive? This Sanctuary is my home. Here I have the safety and love I've searched for all my life."
- Sithis: "Sometimes, right before a kill, Sithis speaks to me. He whispers in my ear and fills my heart with the joy of suffering and death."
- Rumors: "Don't tell anyone else, but some day I'm going to have Ocheeva's position. Just you wait and see. Lucien Lachance knows real talent when he sees it."
- Antoinetta Marie is a reference to Marie Antoinette, a former queen of France who was executed at the age of 37.
- The Hero can find a note in the room of Ocheeva's Chest from Vicente Valtieri about his disease to garlic as she had done a meal with garlic in it.
- Out of all the members, she is the most friendly during the Hero's first meeting.
- She may be in a relationship with Mathieu Bellamont as she receives a letter, from him, (as anonymous) to leave the sanctuary as he knows about the purification that is about to occur.