NXIVM head Keith Raniere was sentenced to 120 years in prison this week for turning some female followers into sex slaves.
Ex-follower and whistleblower Sarah Edmondson spoke to RNZ and said "the world is now a better place" with Raniere behind bars.
Raniere was last year convicted of racketeering, sex trafficking, child pornography possession and other crimes.
The punishment was handed down on Tuesday by a District Judge in Brooklyn after a sentence hearing where former members of the cult spoke out against him.
As leader of the group, Raniere recruited women as slaves and forced them to have sex with him - and even branded some of his inner circle with his own initials.
Edmondson, a former follower, has has since written a book about her experiences - Scarred: The True Story of How I Escaped NXIVM, the Cult That Bound My Life.
"It's closure after over three years of incredibly painful, traumatic, challenging, arduous time spent trying to shine light on this guy and his atrocities and it feels like all of that work has paid off," she said.
Edmondson publicly denounced NXIVM in 2017, revealing that she had been invited to join "DOS" - or Dominus Obsequious Sororium - a secret smaller group operated by Raniere and Smallville actor Allison Mack. DOS was operated out of Mack's home in Albany, New York, and Edmondson said it was here that she was branded with Raniere's and Mack's initials.
Describing Raniere as "sociopathic, narcissitic and sex-addicted", Edmondson believes the outcome of NXIVM was what the leader had in store all along.
"Knowing what we know now, I believe that when he started this company, I say that loosely, in 1998 this was always his goal.
"His intentions were always bad, he was just really smart at creating a really good personal development program that was an excellent shroud for his desires."
She said the main reason Raniere was eventually caught was because he got "greedy and sloppy" - and others had tried and failed to bring him down in the past.
"I think that if he hadn't started DOS and putting his initials on women's bodies he'd still be operating and his abuses would be harder to pinpoint," she said.
"Many people before me have gone to the FBI and to the local law enforcements to say there's something shady going on here, and unfortunately the people who came forward then had law enforcement go after them."
After Edmondson made her initial allegations, hundreds of loyal members and thousands who were loosely affliated with NXIVM left the group.
"I ran the Vancouver centre and what we had there was a very special community of likeminded people wanting to work on their goals and be the best versions of themselves and supporting each other in their goals and dreams.
"And when we found out, it was a huge shock. In fact, we're still finding out the atrocities he committed because he kept it so hidden and so secret."
But with Raniere now facing a lifetime in prison, Edmondson said he might now be able to use some of the techniques he taught group members.
"One of the tools he taught us was to look at any particular area of your life that you were unhappy with and you could always ask yourself, how did I cause this, how did I participate, or his words were 'how did I author this'", she said.
"So the irony is, he's got 120 years to sit there and figure out how he authored himself being in prison."