NXIVM founder Keith Raniere convicted of all charges in sex cult case “It was a horror movie,” said one ex-member who spoke to ABC News' '20/20'.

NXIVM’s founder Keith Raniere was convicted on Wednesday on all seven counts against him, for creating what prosecutors described as a sex cult in which female members were branded with his initials and kept in line through blackmail.

Raniere, 58, was convicted after a six-week trial of charges including racketeering, racketeering conspiracy, wire fraud conspiracy, forced labor conspiracy, sex trafficking, sex trafficking conspiracy and attempted sex trafficking. He will be sentenced Sept. 25.

Raniere, also known as "Vanguard" to members within NXIVM, and Allison Mack, who is best known for her role on the TV series "Smallville," were both indicted by a grand jury in April 2018 on charges arising from Raniere and Mack’s alleged roles in a secret society within NXIVM.

Rainere did not testify at trial and his defense attorney did not call any witnesses, but contended in court that the relationships were consensual, not forced.

According to the United States Attorney for the Eastern District of New York Richard P. Donoghue, Mack recruited women into what they believed was a "female mentorship group that was, in fact, created and led by Keith Raniere."

Raniere was portrayed as a leader, a mentor, guru, humanitarian but prosecutors called him "a conman, a predator, a crime boss."

Prosecutors say many of the female victims were branded and forced to participate in sex acts with Raniere.

Outside court, Donoghue called Raniere a "Master manipulator, a conman and crime boss of a cult-like organization involved in sex trafficking, child pornography…branding…and humiliation."

"His crimes, and the crimes of his co-conspirators, ruined marriages, careers, fortunes and lives," Donoghue said.

According to the criminal complaint from the Department of Justice, "in 2015, Raniere created a secret society within Nxivm called ‘DOS,’ which loosely translated to ‘Lord/Master of the Obedient Female Companions,’ or ‘The Vow.’ DOS operated with levels of women ‘slaves’ headed by ‘masters.’ Slaves were expected to recruit slaves of their own (thus becoming masters themselves), who in turn owed service not only to their own masters but also to masters above them in the DOS pyramid. Raniere stood alone at the top of the pyramid. Other than the (sic) Raniere, all members of DOS were women."

Prosecutors asserted that Raniere had more than 50 DOS slaves under him, many of whom were recruited from within NXIVM’s ranks.

"As alleged, Keith Raniere displayed a disgusting abuse of power in his efforts to denigrate and manipulate women he considered his sex slaves," FBI’s New York Field Office Assistant Director-in-Charge William F. Sweeney Jr. said in a statement in March. "He allegedly participated in horrifying acts of branding and burning them, with the cooperation of other women operating within this unorthodox pyramid scheme. These serious crimes against humanity are not only shocking, but disconcerting, to say the least, and we are putting an end to this torture today."

After reports started surfacing about DOS last year, a letter was posted on the NXIVM website, in which Raniere said, "The picture being painted in the media is not how I know our community and friends to be, nor how I experience it myself. However, as an organization and as individuals, we felt it was imperative that we hire experts to ensure there is no merit to the allegations."

"Additionally, I feel it is important to clarify the sorority is not part of NXIVM and that I am not associated with the group," the statement continued. "I firmly support one’s right to freedom of expression, so what the sorority or any other social group chooses to do is not our business so long as there is no abuse. Our experts, a forensic psychiatrist of international repute, psychologists and ex-law enforcement, say members of the sorority are thriving, healthy, happy, better off, and haven’t been coerced. Furthermore, the sorority is proud of what they created and want to share their story. I am confident they will be addressing you very soon."

ABC News' "20/20" did an extensive report on NXIVM last year, including interviews with several former members, including Sarah Edmondson, who said she was a member of the group for over a decade.

Edmondson told ABC News and said in a complaint to the New York State Department of Health that after attending NXIVM seminars for more than a decade, she was approached about an opportunity to join a secret sorority. Then, one night she said she and five other women were summoned to a house in the Albany area, where they thought they were going to get a tattoo but once there, found out she and the other women were going to be branded.

"It was a horror movie," she told "20/20." "It was the most inhumane, horrific way to treat anybody. But the most horrific thing is that it’s women doing it to women."

Edmondson said each of the women would lie down naked and then was branded with a cauterizing device, without any anesthesia. When it was her turn, Edmondson said the pain felt "worse than childbirth."

ABC News' Lauren Effron contributed to this report.