A former “slave” in the cult-like group NXIVM testified in court Wednesday she was sexually assaulted by founder Keith Raniere after her female master ordered her “to seduce him.”

“I follow Keith into the house and he took me straight upstairs,” the woman, identified by prosecutors only as Sylvie, told jurors in Brooklyn federal court on Wednesday . “He told me to undress and lie on my back on the bed. He then went down on me and I just remembered it felt like it was going on for a really long time.”

Raniere, 58, is accused of running a sex-cult pyramid scheme that branded and enslaved women while promoting NXIVM as a self-improvement organization to the public. He is charged with sex trafficking, racketeering conspiracy, child exploitation, and child pornography. Raniere has pleaded not guilty to all the charges.

Sylvie, a 32-year-old native of Britain, first became involved with NXIVM in 2005. Then an 18-year-old professional horse jumper, she was invited to the farm of Seagram liquor heiress Clare Bronfman. The farm, she later learned, was connected to NXIVM headquarters in nearby Albany, New York and Brofman was the group’s operations director and one of its largest donors.

She was quickly indoctrinated into the community after Brofman paid for her 16 self-fulfillment intensive courses, which cost about $3,500 and included a nondisclosure agreement that required members refer to Raniere as “Vanguard.”

Over the next decade, Sylvie’s continued an on-and-off relationship with NXIVM while she continued a career as a horse jumper, and later a professional runner under the coaching of Raniere.

In 2015, fellow NXIVM member Monica Duran offered her the chance to join a elite “master-slave program” that would help her “overcome her fears” by submitting herself to Duran’s orders.

“ The whole time was filled with lies, secrets, and darkness. ” — Sylvie

The program was a secret sorority known as DOS, which prosecutors allege “slaves” would allegedly be forced to have sex with Raniere and brand themselves with his initials near their crotch with a cautery pen without anesthesia. In opening statements on Tuesday, Raniere’s attorney Marc Agnifilo called DOS a “women’s organization” Raniere felt women needed.

Her first assignment was to send Raniere explicit photos of herself to an attempt to “seduce him,” which were accidently seen by her father. After asking Duran if she could stop sending the photos, Sylvie was ordered to meet Raniere in person so he “could take [her picture].” If she didn’t comply, Sylvie said Duran would release her “collateral,” a handwritten letter addressed to her parents falsely claiming she was a prostitute.

Meeting her outside the house, Raniere brought her into a room upstairs with a “big bed with white dirty sheets” and told her to undress.

“I was terrified but I knew what I had to do,” she testified Wednesday while Raniere watched emotionlessly from across the courtroom in a blue sweater and white button-down shirt. “I made sounds I thought I should be making so it would finish.”

“It was a whole different realm of darkness,” Sylvie added Wednesday, fighting back tears. “I felt so much shame and I still do honestly. The whole time was filled with lies, secrets, and darkness.”

When asked by the prosecution if she wanted to “participate,” Sylvie said “no, but it was a command from my master.”

Sylvie said she first thought NXIVM was too “touchy feely” and so “spooked” after her first day of classes, she threw up.

“The girls are very focused on food and their weight,” she said. “On my first day there, they took me to lunch and I got a slice of pizza and they didn’t eat anything.”

On the second day of the training, Sylvie took a class called “suppressives,” in which NXIVM’s co-founder Nancy Salzman taught about people who try to tear down those around them. Sylvie testified she related to what Salzman was teaching and “became very motivated because I was afraid I might be a bad person.”

Sylvie left NXIVM in 2017 after the news broke of that DOS was physically and sexually abusing women.

She finished testifying Wednesday, emphasizing that many in the community had a hard time believing DOS’ existence or hoffiic allegations because “many thought that the women were lying just like we were taught.”