India Oxenberg Was 'Afraid' of Former Nxivm 'Master' Allison Mack — 'But She Can't Hurt Me Anymore'

It was in January 2015 when Allison Mack, the Smallville actress and most well-known member of the now notorious cult Nxivm, quietly approached India Oxenberg: She wanted her to join a secret sorority within the group, which she described as a "sisterhood."

"Allison said she had a special program she thought could help me," India tells PEOPLE. "I felt singled out. I felt special."

By then, India was deeply entrenched in the group, having endured four years of indoctrination and brainwashing.

Mack told India the secret group was called DOS (for the Latin phrase Dominus Obsequious Sororium, roughly translated to "Master Over Slave.") And within the sinister "sisterhood," Mack would eventually become India's master, the one who demanded "ultimate obedience."

Now 29, India is sharing her harrowing story for the first time in the powerful STARZ four part docuseries Seduced: Inside The Nxivm Cult, which begins airing October 18, at 9 pm EST/PST.

"I knew too much about what happened," says India, "and I had a moral obligation to make sure it didn't happen to anyone else."

When Mack told her about DOS, she said she needed "something to make sure I wouldn't share what she was about to disclose," India recalls. "That's how I ended up providing her with collateral. In reality, it was like I handed over the keys to lock myself in prison."

RELATED: Catherine Oxenberg's Daughter India Recalls Harrowing Moment She Was Branded in Nxivm Sex Cult

At first, the "collateral" involved divulging family secrets and taking nude photos, requests that became more and more graphic. India, by then living with Mack in Albany, New York, where the group was headquartered, had to cook and clean for her, and eventually starve herself in accordance with her demands.

"She said I could have no more than 500 calories a day," says India.

By that point, India was so run down by Nxivm's endless classes — called "the curriculum" — the lack of sleep and little food that she had lost the ability to think critically and independently.

What she didn't realize was that she was being groomed to become a sexual partner for Nxivm's leader, Keith Raniere. "One of my first commands was to seduce Keith," she says. "Allison said it was to make me feel less vulnerable. And I wanted to believe her."

RELATED: Nxivm Founder Keith Raniere Guilty in Sex Trafficking Case Involving Smallville's Allison Mack

If she failed in her tasks, India faced punishment, dictated by Mack.

"You get so used to this environment of abuse that you believe you're deserving of it, that it's good for you," says India.

For more on India Oxenberg's journey out of Nxivm, subscribe now to PEOPLE or pick up this week’s issue, on newsstands Friday.

Looking back she says, "I didn't want to see it as sexual abuse. I feel shame and embarrassment about what happened but I also have forgiveness for myself. Women who experience this kind of abuse do strange things in their mind to be okay with it."

RELATED: WATCH: Allison Mack Extols Women's Self-Help Group Years Before She's Accused of Recruiting Sex 'Slaves'

According to India's therapist Rachel Bernstein, who also participated in the STARZ docuseries, "When people are groomed, they feel they have been specially chosen. What you don't realize is the true intention of the grooming. It seems like you've been chosen for something special and the whole point is for you to lower your defenses, and when you lower your defenses, you lower your boundaries and they can much more easily manipulate you and abuse and exploit you."

Catherine Oxenberg exposed cult

It was India's mother, former Dynasty star Catherine Oxenberg, who went public with her fight to save her daughter in 2017 — and who sounded the alarm about Raniere and his cult.

"I was terrified," says Catherine, a mom warrior who told the dramatic story in her 2018 book, Captive. "But that didn't matter. I had to do it. I didn't have a choice."

In the course of her efforts, she amassed a trove of documentation, and in 2018 met with prosecutors to share her findings, which aided the investigation into Raniere and led to his arrest in March 2018. Found guilty on charges including sex trafficking, racketeering and possession of child pornography, he will be sentenced on October 27 and faces up to life in jail.

RELATED: Catherine Oxenberg Is Writing a Book About the Group She Claims 'Brainwashed' Her Daughter

Once he and his top lieutenants had scattered, India says, "that separation created a little space for me to start to question, but I had to be careful because I knew what they did to people who left Nxivm: character assassination or litigating them into oblivion."

And she began to break free from Mack, who was arrested in April 2018 and later admitted to conspiracy, extortion and forced labor. She now awaits sentencing.

Looking back, says India, "Allison had a lot of power and control over me and I was always trying to accommodate her. That's how I protected myself, but now she can't hurt me anymore."

The STARZ four-part docuseries, Seduced: Inside the Nxivm Cult, begins airing Oct 18 at 9 p.m. EST/PST.

Watch the full episode of Catherine and India Oxenberg: Surviving NXIVM streaming now on PeopleTV.com, or download the PeopleTV app on your favorite device.