is gathered from the Matrix to present a case against the Doctor on charges of breaking the first law of time. This is done by the Valeyard, a learned Court Prosecutor. It transpires however, that the Valeyard has been able to tamper with the events shown by the Matrix to produce false evidence against the Doctor. When this is revealed by the Master, the Valeyard flees to a virtual reality world created by him within the Matrix. Within the Matrix, the Doctor is forced to fight the Valeyard, much like he had fought Goth in The Deadly Assassin. The Valeyard's world appears as a Victorian factory, and he is disguised as a Mr Popplewick. The Master is also able to materialise his TARDIS inside the virtual reality within the Matrix. Together the Master and the Doctor manage to defeat the Valeyard and discover his plan to murder the Time Lords at the trial with a Particle Disseminator. In the revived series, though it seemed that they were destroyed, it was revealed that both Gallifrey and the Time Lords were removed from the known universe at the end of last great Time War. The fate of the Matrix was uncertain at the time as the Master returned to Gallifrey on its final day at the climax of "The End of Time". In "Dark Water", it is revealed that the Master, now in the form of Missy, created a Matrix called the Nethersphere to upload and edit the minds of recently dead humans before re-entering them into an upgraded Cyberman body. The Matrix is a key element of the plot of "Hell Bent". When the Doctor returns to a resurrected Gallifrey, he extracts Clara from her timeline seconds before her death and the pair enter the cloisters of the Citadel where the Matrix is located, attempting to steal a TARDIS capsule from the workshop below. The Matrix is guarded by Cloister Wraiths and captured Daleks, Cybermen and Weeping Angels—the Doctor describes it to Clara as "a big computer, made of ghosts, in a crypt, guarded by more ghosts". Other appearances The following section contains information taken from spin-off material. The canonicity of these stories with regard to the television series and each other is open to interpretation. In the Doctor Who comic strip published in Doctor Who Magazine, the Matrix is depicted as being inhabited by the minds of dead Time Lords—including