Sean 'Diddy' Combs' ex-girlfriend Cassie Ventura is set to testify against his him in his sex-trafficking and racketeering trial in Manhattan federal court.

The disgraced music mogul, 55, is accused of leading a criminal enterprise for 20 years, using his fame and wealth to coerce and threaten women into submission.

On Monday, the jury heard harrowing testimony from Daniel Phillip, a male escort who testified that he was paid thousands of dollars to have sex with Cassie as Diddy watched.

Phillip recalled witnessing the rapper physically abuse Cassie on multiple occasions and added that the music mogul once gave him MDMA.

His testimony came after the court heard how Combs forced women to take part in drug-fueled sex parties which went on for days while he filmed them.