Dark Matrix

The legendary Dark Matrix was a repository of all the dead Time Lords' most evil, twisted and perverted thoughts. It was the antithesis of the Matrix. The Doctor confronted the Dark Matrix when the Valeyard - attempting to use its power to give himself a new body - had trapped it inside his TARDIS, 'feeding' it the energies of the women he killed under his new alias of the Ripper to try and control it, the Doctor provoking the Dark Matrix into destroying the TARDIS and itself by convincing it that it was still a prisoner. (PDA: Matrix)