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