Sylvie, who grew up in Britain, came to the United States when she was 18 and lived on a farm where she took care of horses belonging to Clare Bronfman, the Seagram’s liquor heiress who was a high-ranking member of Nxivm.

Over the next decade the group exerted a pull on her, according to her testimony. At one point, she said, Mr. Raniere suggested she leave a job she had obtained with Goldman Sachs. Ms. Bronfman also told her she would have to quit a running club she was part of.

Sylvie testified that she joined a Nxivm-related group called Jness that she said espoused, among other things, that women were victimizers who liked to pose as victims.

“I started to hate the fact that I was a woman,” she said.

By the time Sylvie was invited to join D.O.S. — the initials are an acronym for a Latin phrase that roughly translates to “Lord/Master of the Obedient Female Companions” — she was eager to join, she testified. She thought it might help her improve as a person, she said, even though she had no idea what being part of the group would entail.

She said she provided collateral in the form of a letter where she claimed to her parents that she was a prostitute.

In her roughly two years with D.O.S., Sylvie said, she followed any directive given to her by Ms. Duran, including the order to recruit “slaves” of her own and obtain collateral from them. She was also compelled by Ms. Duran, she said, to provide additional collateral of her own, including a letter that gave Ms. Duran the power to say whether or not Sylvie could have children.

Ms. Duran directed Sylvie to walk her dog, pick up her prescriptions and do her grocery shopping, she testified. She said Ms. Duran also gave her a necklace called a “dog collar” that was meant to symbolize their relationship and came with what was supposed to be an unbreakable clasp.