Larry Ellison, the largest outside financial backer of Musk's deal to take over the social media company, was subpoenaed as part of the lawsuit against Musk.
Ellison was subpoenaed as part of the lawsuit over Musk backing out of his purchase of the company.
Ellison, a long-time Musk ally and a board member from this year to this year, pledged $1 billion to the CEO of the electric car company through his trust.
The trust's official was subpoenaed by the social network last week.
Forbes did not get a response from representatives for Ellison.
The company accepted Musk's proposal to take the company private. Musk filed paperwork July 8 to pull out of the deal over claims that the company did not give proper data about the number of accounts on the platform. A Delaware judge is being asked to force Musk to close the deal after he withdrew.
Ellison is the sixth wealthiest person in the world. Ellison has a 1.5% stake in the company. The largest fortune in the world is held by Musk.
The trial between Musk and the social networking site will last five days. The case promises a lot of drama, and Bill Savitt, the top lawyer in the case, called Musk a liar during a virtual hearing to set the trial date.
The company won a bid for a quick trial.
Larry Ellison was subpoenaed in the Musk buyout battle.
Larry Ellison gave $1 billion for Musk's takeover of the social networking site.