You may be looking for the Crown of Rassilon.

The Coronet of Rassilon was one of the many artefacts created by Rassilon, similar to the Crown of Rassilon.

When worn, the Coronet enabled domination over the will of others. Lord President Borusa used the Coronet to impose himself on the Fifth Doctor, but this was broken by the mental power of the First, Second, and Third Doctors. Borusa also paralysed the Brigadier, Sarah Jane Smith, Susan Foreman and Tegan Jovanka when he told them not to move or speak until spoken to; they were freed when Borusa was imprisoned within Rassilon's sarcophagus. (TV: The Five Doctors)

The Coronet was part of the Matrix. (AUDIO: Imperiatrix)

Attending the opening of a new Capitol building as Lord President, the Fifth Doctor donned the Coronet of Rassilon as part of a Presidential dress he was forced to wear. (AUDIO: Time in Office)

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