The Recorder

 was used by Rassilon to record his scientific projects.

While dealing with the aftermath of the explosion of Anti-Time, the TARDIS created a series of holographic projections, taken partly from reality and partly from the memories of the Eighth Doctor, Charley Pollard and the TARDIS itself. One such projection was the meeting in Rassilon's Foundry as the TARDIS was looking for information on the Divergence. Inside this projection, it placed Charley in the role of Rassilon and itself in the role of the Great Vampire Arata. The projection of the Recorder was created using the voice of the Sixth Doctor's companion Frobisher. (AUDIO: Zagreus)