One of the Doctor’s deadliest foes has returned after hiding in plain sight on the show.

It was Sylvester McCoy’s Seventh Doctor, who summed up the Rani perfectly. “Don’t underestimate her,” he said in the episode Time and the Rani. “She’s a brilliant but sterile mind. There’s not one spark of decency in her.”

Her main interest is science, but she is willing to hurt and kill for her research.

In an interview with the BBC, actor Kate O’Mara described the character as someone who attended university with the Doctor, “studying science. And then it went completely to her head, and she wanted to govern the whole universe.”