Fausta

You may be looking for Faust.

Empress Fausta was the wife of Emperor Constantine. She was politically adroit and active — a dangerous combination that eventually led to her downfall. Whilst the Council of Nicaea was ongoing in 325, she spent a lot of time with Peri, who was confined to Constaintine's court as a sort of ransom for the Fifth Doctor's good behaviour. She tried to use the opportunity to talk to the Doctor, whom she imagined fascinating. She also tried to slyly figure out where Erimem, then wanted by her husband, had gone. Ultimately, she didn't succeed in either ambition.

Years after the Council, Constantine steamed her to death in her own bathroom because he thought she was working against him. The Doctor believed that Constantine's suspicions were probably well-founded. (AUDIO: The Council of Nicaea)