The Grammy-winning musician Scott Mescudi, known as Kid Cudi, called the rapper Sean “Diddy” Combs, who is on trial fighting sex trafficking and other charges, a “Marvel supervillain” during his testimony on Thursday. The witness had a brief affair with Mr. Combs’s then-girlfriend, Cassandra Ventura. He claimed that when Mr. Combs found out about the affair, the mogul’s henchmen broke into Mr. Mescudi’s home and bombed his Porsche Cabriolet with a Molotov cocktail.

Next week, prosecutors plan to call a former employee of Mr. Combs who communicated with Mr. Mescudi during that time, signaling that they are not done establishing the allegations related to Ms. Ventura, the prosecution’s star witness who testified last week.  

“Sean Combs was standing there staring out the window with his hands behind his back like a Marvel supervillain,” Mr. Mescudi, 41, testified as he described a meeting with the defendant in January 2012 at Soho House in Los Angeles. 

The multi-platinum singer, songwriter, actor, and rap artist, who entered the courthouse puffing a cigarette in the morning, had been called to the witness stand to answer questions about his allegations that Mr. Combs had his Porsche firebombed, destroying the sports car completely, and also that he orchestrated a break-in to his home, because Mr. Combs was jealous that Mr. Mescudi was having an affair with his on- and off-again girlfriend, Ms. Ventura. 

Mr. Mescudi told an assistant United States attorney, Emily Johnson, that when he started dating Ms. Ventura in 2011, he was under the impression “that she and Sean Combs had some problems and they weren’t dating anymore.”  

But then in December 2011, Mr. Mescudi testified, he got a frantic phone call early in the morning from Ms. Ventura, saying Mr. Combs had found out about their relationship.   

“I got a call from Cassie around 5:30, 6 a.m., but she asked me to pick her up. She sounded really stressed on the phone, nervous, scared, so I went to go pick her up. … She told me that Sean Combs had found out about us. I was really confused,” he went on and when asked by Ms. Johnson why he was confused, he said, “Because I didn’t think she was still dealing with him.”   

He said, “She wanted me to come pick her up. And she was also worried that he would come to my house because he asked for my address and she gave it to him.” 

Mr. Mescudi said he went to pick Ms. Ventura up and then, as he was driving to take her to a hotel that he felt she was “safe,” he got a phone call from one of Mr. Comb’s employees, Capricorn Clarke, who was, according to him, friends with Ms. Ventura and had been “hanging out” with them. 

Ms. Clarke, he said, told him that the defendant “and an affiliate” were at his house and that she “was forced to go along with them over there.” 

Then, he called Mr. Combs directly. “I said, ‘Motherf—, you in my house?’ And he was like, ‘What’s up?’ I was like, ‘Motherf— are you in my house?’ And he said, ‘I just want to talk to you.’ I was like, ‘I’m on my way over right now.’ He was like, ‘I’m here.’” 

When Mr. Mescudi got back to his home in the Hollywood Hills, Mr. Combs was nowhere to be found. But the security cameras were not working, because he said somebody moved one of the cameras, so the “camera that was angled down at the door originally, was moved to an opposite angle.” 

Inside his house, the singer found that gifts he had bought for his family “were opened” and that his dog was “locked up in my bathroom.”  Mr. Mescudi called the police and filed a report about the break-in. 

Mr. Mescudi said he spent the holidays with Ms. Ventura, and stayed with her at her family’s home in Connecticut, where their relationship ended. Mr. Mescudi returned to Los Angeles before New Year’s. This corroborated Ms. Ventura’s testimony from last week, when she told the jury that she ended the relationship because she was afraid Mr. Combs would hurt her or Mr. Mescudi if they kept seeing each other. She said that Mr. Combs threatened Mr. Mescudi’s life and that he was going to blow up Mr. Mescudi’s car, though “not by his hands.”

Mr. Combs kept sending Mr. Mescudi text messages, he said, wanting to talk, but after the breakup Mr. Mescudi didn’t respond to the texts. He said he was upset that Mr. Combs had “messed” with his dog.     

In January 2012, Mr. Mescudi went on to testify, someone did in fact blow up his Porsche 911 Cabriolet in his driveway. He got a phone call, he said, at 6:30 a.m. from his dogsitter, saying that his car was on fire. Mr. Mescudi was staying at his “ex-girlfriend’s sister’s house.”  

He drove to his house and when he arrived he said that “the top of my Porsche was cut open and that’s where they inserted the Molotov cocktail.” He saw the bottle in the burnt-up car on the driver’s seat. The car was beyond repair. The jury was shown photos of the car, which confirmed the detrimental damage. 

“I reached out to Sean Combs after my car had caught fire and, you know, finally told him that we needed to meet up to talk, you know. He had been wanting to talk to me. So after the fire I was like, this is getting out of hand. I need to talk to him,” Mr. Mescudi said.  

That’s when Mr. Mescudi and Mr. Combs scheduled the meeting at the Soho House, because he felt like things were getting out of hand. When he asked Mr. Combs about what happened to his car, Mr. Mescudi said Mr. Combs replied that he didn’t know what he was talking about. Mr. Mescudi testified that he believed the defendant was lying.

Mr. Mescudi said the last time he saw Ms. Ventura, who went back to dating Mr. Combs, was at a private club in Los Angeles shortly after his car was destroyed in 2012. He testified that they “just stopped talking” after they had kept in touch every day for almost a year.

He told the defense attorneys during cross-examination that he felt “upset” when he found out that Ms. Ventura went back to her relationship with Mr. Combs. 

“I was upset to find out that she had kind of went back to him,” he told the defense attorney during cross-examination. 

He also told prosecutors that he eventually made peace with Mr. Combs after he apologized in 2015, when he ran into Mr. Combs at the Soho House with his daughter.  

“He was with his daughter, and he pulled me to the side and basically apologized for everything. He said, and I quote: ‘Man, I just want to apologize for everything and all that bulls—.’ … After I got the apology, I kind of found peace with it because I thought, you know, that was the last thing I was expecting to get from him.”  

The trial will not resume until May 27, due to the Memorial Day holiday. Prosecutors said that they intend to call Ms. Clarke, the employee who was friends with Ms. Ventura and called Mr. Mescudi the night “someone” broke into his home.