The Valeyard

"There is some evil in all of us, Doctor – even you. The Valeyard is an amalgamation of the darker sides of your nature, somewhere between your twelfth and final incarnation, and I may say you do not improve with age."

- The Master to the Sixth Doctor about the Valeyard.

The Valeyard is the main antagonist of the 14-part Doctor Who serial "The Trial of a Time Lord". He is a lawyer and a future incarnation of the Doctor himself.

He was portrayed by Michael Jayston.

History
As the Valeyard doesn't have much regenerations left, he wanted to get the Doctor accused in a trial for death penalty. However, the Master appeared in the trial to point out that the Valeyard was actually the Doctor himself, which made him flee the trial into the Matrix, where the Doctor followed him. In the end the Doctor could escape the death sentence, but also the Valeyard was able to escape.

Trivia

 * The Valeyard is a mix of the darkest sides of the Doctor, just like the Dream Lord