A NXIVM recruit testified in a Brooklyn courtroom Thursday that “Smallville" actress Allison Mack ordered her to lie about her father sexually abusing her so that the alleged sex cult would have blackmail against her, according to a report.

The woman, who was identified as Nicole, said that as top NXIVM lieutenant, Mack, ordered her to write a letter with the made-up story so that the cult would have “collateral” to secure her “lifetime commitment,” the New York Daily News reported.

'SMALLVILLE' STAR ALLISON MACK MAY TESTIFY AGAINST ALLEGED NXIVM SEX CULT LEADER: REPORT

“I couldn’t write anything,” Nicole testified at the federal trial of NXIVM leader Keith Raniere. “Like, my family is amazing. I love my family,” she said to jurors as her parents were also in the courtroom.

Keith Raniere (left) and his accused sidekick, "Smallville" actress Allison Mack, are also being accused of "human smuggling" and "alien harboring." (YouTube/AP)

Raniere, 58, pleaded not guilty to several charges, including sex trafficking and racketeering related to the NXIVM organization based in upstate New York.

Federal prosecutors argue that Raniere ran the sex cult under the guise that it was a self-empowerment group. Lieutenants, like Mack, would slowly coerce young women to become Raniere's sex slaves and brand them with his initials, according to the allegations.

Nicole, a 31-year-old aspiring actress from California, testified that she first met Mack at an acting class. She said Mack first told her NXIVM was a women’s empowerment group and began to set her up with off-Broadway auditions and acting agents.

Things took a darker turn when Mack allegedly instructed Nicole to remain celibate for three months. The 36-year-old actress eventually told Nicole to make a solo sex tape as a part of collateral for NXIVM, according to the testimony.

“It was an exercise in trust,” she said Mack told her. “No one is going to see any of this.”

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Mack pleaded guilty to racketeering charges related to NXIVM and is scheduled to be sentenced on September 11. Mack is best known for her long-running role on the superhero TV show about the early days of Clark Kent’s life.

Fox News' Tyler McCarthy and Jessica Sager contributed to this report.