Allison Mack, the former “Smallville” actress, was sentenced to 3 years in prison Wednesday in a Brooklyn federal court for her role in the so-called sex-trafficking cult, NXIVM.

Mack, who has been under house arrest in California since her April 2018 arrest, pleaded guilty to racketeering and racketeering conspiracy charges in April 2019. She was also fined $20,000 and ordered to surrender by late September.

With her plea, Mack admitted she gave “seduction assignments” to several women in the secret NXIVM sub-group DOS, which stands for a Latin phrase loosely translated as “master over the slave woman.” Women in DOS were told they would be joining a secret women’s sorority.

In reality, Mack was among eight “first-line slaves” who reported directly to Keith Raniere, the leader of a Capital Region cult named NXIVM. “First-line slaves” were encouraged to recruit their own “slaves,” thus becoming their “master.”

Raniere was sentenced in October 2020 to 120 years in prison after being found guilty of a number of crimes, including sex trafficking and forced labor conspiracy.

Three years after her arrest, Mack, 38, now calls NXIVM leader Keith Raniere, the man she once looked at as her guru, “twisted.”

Mack had four “slaves” that she regularly required to submit damaging collateral, including naked photographs. The women were not told of Raniere’s involvement in DOS when they joined.

One of Mack’s “slaves” testified during Raniere’s trial that she was instructed by Mack to meet Raniere outside. He then blindfolded the woman, taking her to an unknown location, where she received oral sex from an unknown person. It was later discovered the sexual act was performed by a different “first-line slave."

Another woman testified she was given an assignment by Mack and another DOS member to seduce Raniere. She refused to do so, and fled the group soon after.

Despite sentencing guidelines ranging from 14 to 17 1/2 years, prosecutors recommended Mack be given less time due to her “substantial assistance” and cooperation with the investigation against Raniere and other NXIVM co-conspirators.

Mack provided emails, documents and recordings to the government.

While Mack was not called to testify, prosecutors say she was prepared to do so.

It was previously unknown what Mack’s cooperation level with the government had been. Raniere told the court during his sentencing that she did work with investigators in the case against him. That information had previously not been made public.

Mack’s attorneys say since pleading guilty, she has received her associate’s degree and enrolled in courses at the University of California, Berkeley. She has also become active in a local church.

Seagram’s heiress Clare Bronfman, who pleaded guilty to charges involving fraud and identity theft, was sentenced in September 2020 to 81 months in prison. She was the first NXIVM co-conspirator to be sentenced for their role in NXIVM. Other co-conspirators, including NXIVM co-founder Nancy Salzman, member Lauren Salzman and bookkeeper Kathy Russell, await their sentencings.

Lauren Salzman will be sentenced July 28. The remaining sentencings have not been scheduled.

Raniere and other members of NXIVM resided in Halfmoon, and initially conducted operations out of an office in Colonie.

NXIVM has inspired several documentaries, including “The Vow” on HBO and Seduced: Inside the NXIVM Cult on Starz. A second season of the HBO series is expected to air later this year.