This is two years after your initial posting, but I do have a copy of the Bill filed in the case of Maria &c v. Moore in Prince Edward Superior Court in 1810. Your ancestor, Dennis, appears to be one of the plaintiffs in the initial filing for freedom, and yes there were more than 40 defendants involved in the suit.

My source for the following excerpts is the article entitled "Superior Court Judgement, 1814" from Southside Virginian Vol. 8, Issue 2, April 1990.

[Bill]. Maria alias Murrier & Douglas for themselves and the following persons infants to wit: Tyler, Sam, Robin, Phebe, John, Fanny, Anthony, Dennis, Judy, Royall, Douglas, Lizzy, Phebe, Henry, John, Lymus, Lewis, James, Sterling, Stephen, Billy, Thornton, Maria, George. Winny, Drury, Cephas, Polly, Billy, Berry, Dick, Jack, Salley, Jenny, Anthony, Eliza, Tilla, Royall, Dennis, Molly, Henry, and Aggy complain of Molley Moore. Defts. unlawfully did assault and detain pltfs. in 1810 and they sue for damages of $50,000.

The petition states that the above minors are children and grandchildren of Maria, alias Murrier. That Maria is the daughter of Tab who was the daughter of Maria or Murrier a free Indian woman. That Douglas is a son of said Maria or Murrier first above mentioned and all the others are lineally descended in the female line from the aforesaid free Indian woman Maria or Murrier and are held in slavery by Mary Moore. They pray to be allowed to sue for freedom in forma pauperis.