Baron Mordo first appears in the Spider-Man: The Animated Series episode "Sins of the Fathers Chapter 1: Dr. Strange" voiced by Tony Jay.
Baron | William Cecil, 1st Baron Burghley | baron | Sacha Baron Cohen | Joseph Lister, 1st Baron Lister | Joey Baron | Robert Baden-Powell, 1st Baron Baden-Powell | Henry Brougham, 1st Baron Brougham and Vaux | Guy Carleton, 1st Baron Dorchester | William Wallace, Baron Wallace of Saltaire | William Tyssen-Amherst, 1st Baron Amherst of Hackney | James Mackay, Baron Mackay of Clashfern | Hercules Robinson, 1st Baron Rosmead | George Brydges Rodney, 1st Baron Rodney | Beechcraft Baron | Thomas Seymour, 1st Baron Seymour of Sudeley | Thomas Denman, 1st Baron Denman | Stuart Rendel, 1st Baron Rendel | Norman Foster, Baron Foster of Thames Bank | John Moore-Brabazon, 1st Baron Brabazon of Tara | Charles Cochrane-Baillie, 2nd Baron Lamington | Charles Calvert, 5th Baron Baltimore | Benedict Calvert, 4th Baron Baltimore | Baron Hans Heinrich Thyssen-Bornemisza | William Ponsonby, 1st Baron Ponsonby | Walter Rothschild, 2nd Baron Rothschild | Sidney Herbert, 1st Baron Herbert of Lea | Robert Napier, 1st Baron Napier of Magdala | Martin Conway, 1st Baron Conway of Allington | John Reith, 1st Baron Reith |
The heroes are based there up until the mission in the Valley of Spirits, after which they relocate to Doctor Strange's Sanctum Sanctorum to cope with the Masters of Evil's access to the magical knowledge of Baron Mordo and Loki.