The Spy Master

The Spy Master is played by friend of Big Finish Sacha Dhawan, who has appeared in many other stories as different characters. However, he also had a fantastic reveal that I admit I never saw coming, in "Spyfall," and reappeared a few times throughout the Thirteenth Doctor's tenure. Since he has a history of working with the company, it's perhaps not surprising that he was able to land his own series as the Master.