The Valeyard's trial

After serving as prosecutor of the Sixth Doctor's trial, the Valeyard was himself placed on trial by the Time Lords.

History
The Valeyard was found by the Time Lords on the moon of Etarho and was captured and ordered to reveal the secret research into regeneration the thirteenth incarnation of the Doctor had allegedly performed there. The Valeyard refused, and as a result, he was placed on trial with a faked charge of having hacked into the Matrix. He asked for the Sixth Doctor to be his defence. The Valeyard told the Doctor and Inquisitor Darkel of his supposed origins, during which he voiced heresy against the limit Rassilon had imposed on regeneration, suggesting it was only a measure of control from Rassilon's side and was possible to break. As a result, he was judged to immediate termination, but he managed to fake his execution by using a hidden Matrix door placed under the dock, and he escaped through it onto the surface of Etarho's moon.

On the moon of Etarho, the Valeyard impersonated the Thirteenth Doctor and tricked the Doctor into taking a bomb from him. The Doctor discovered his ruse, and the Valeyard escaped again by entering another Matrix door. The Doctor assumed that the Valeyard would likely try again at some point to exact revenge on both himself and Darkel, and warned Darkel that it was very likely the Valeyard had received help from someone powerful on the Time Lord council, pointing out that it would have been very difficult for him to sneak a Matrix door into the courtroom all by himself. (AUDIO: Trial of the Valeyard)