Jurors at Sean Combs’s sex-trafficking and racketeering trial have heard gripping testimony from Casandra Ventura, the singer known as Cassie, who described in lurid detail the violence and coerced sex that she suffered at the hand of the music mogul.

On Wednesday, they are set to hear from a second woman, testifying under the pseudonym “Mia,” who prosecutors say had her own harrowing experience with Mr. Combs.

For months before trial, little was disclosed about Mia — then identified only as “Victim-4” — other than that she is a former Combs employee who prosecutors say was coerced into sex with him. In one filing last month, the government redacted virtually an entire page-long passage about her.

But in opening statements this month, lawyers for both sides fleshed out the woman’s profile somewhat. Emily A. Johnson, a prosecutor, described Mia as a former personal assistant whom Mr. Combs “worked to the bone for years.” At some point, she said, he then “forced himself on her sexually, putting his hand up her dress, unzipping his pants and forcing her to perform oral sex, and sneaking into her bed to penetrate her against her will.”

“Mia will tell you how she could not talk about what happened to her until recently,” Ms. Johnson added, “how she wanted to take the secret of what the defendant did to her to her grave.”

Mr. Combs, who has pleaded not guilty to all charges, has denied having anything but consensual sex with women, and his defense team has suggested it will pursue that approach in countering the testimony of Mia when she appears on Wednesday, likely in the afternoon.