Casandra Ventura says she was coerced into sex with male escorts while Sean Combs watched and masturbated. 

If she ignored his calls, his associates found her. 

If she didn't comply with his demands, he beat her viciously.

And on Tuesday, when she saw the pop singer known as "Diddy" in court, lawyers say it was for the first time in years.

Heavily pregnant with her third child, Ventura, an artist widely known as "Cassie," took the stand for marathon testimony against her ex as the star witness in the trial in which prosecutors have accused Combs of heading a criminal sex trafficking ring.

Wearing a long, turtleneck brown dress, camel coat and heeled boots, Ventura told jurors she first met Combs when she was 19 years old, and signed a contract with his Bad Boy record label for a 10-album deal — only one of which ever got made.

Despite a 17-year age difference, Combs kissed her on her 21st birthday, she says, after which she cried and "ran off."

But they would continue to meet to talk about her music career and the relationship eventually turned sexual, she told jurors as Combs, now 55, imprisoned and noticeably aged, watched on.

"I wanted to be around Sean for the same reasons as everyone else at the time," the 38-year-old testified. "He was just this exciting, entertaining, fun guy — that also happened to have, you know, my career in his hands."

In excruciating testimony Ventura detailed how she eventually fell in love with Combs but felt forced to engage in so-called "freak-offs," sometimes days-long sex performances directed by the one-time billionaire in which Cassie was the star, and according to her, the object.

"I was humiliated," she told the court, her voice breaking with tears as her husband observed from the gallery. "I couldn't talk to anybody about it."

"I just felt like it was all I was good for to him."

Combs would direct her to take drugs before the sex that routinely involved male escorts, and she complied, "I was high so there wasn't too much feeling," she told jurors.

Asked by prosecutors if she ever asked that the freak-offs stop, Ventura said she tried, but to no avail.

"Sean is a really polarizing person, also really charming," Ventura said. "It's hard to be able to decide in that moment what you need when he's telling you what he wants."

'Humiliating'

Defense attorneys indicated they intend to show that Ventura was acting as a free adult engaging in what they've cast as unconventional, but consensual, sexual activity.

But Ventura described highly orchestrated performances at the behest of Combs, who she said demanded rooms be stocked with baby oil and lubricant and mood lighting.

He insisted that Ventura dress in sheer outfits and platform heels purchased at sex shops, she said.

At one point, he instructed her to get in an inflatable pool filled with lube and oil while wearing lingerie, she said.

Ventura said the choreographed sex parties took place in New York, Miami, Los Angeles, Las Vegas and Atlanta as well in Ibiza and Turks & Caicos.

"Honestly you name it, we probably did it there," Ventura said.

The drugs were a "buffer" to withstand the "humiliating" and often-filmed sexual encounters, she said.

Near the end of testimony on Tuesday, just the first of several in which Ventura is expected to take the stand, her voice quavered as she recounted a violent encounter at a Los Angeles hotel in which Combs attempted to drag her back to a freak-off she tried to leave.

The disturbing footage — jurors have now seen it some half-dozen times in just the second day of testimony in the government's case — is but one example of the physical abuse Ventura says she withstood over more than a decade of their relationship.

When he was upset, she says, his eyes would "go black — the version of him I was in love with was no longer there."

"Make the wrong face," Ventura told jurors, "and the next thing I knew, I was getting hit in the face."