A Time Lord criminal was known as The Eleven in his eleventh incarnation. He had a regeneration-based mental illness, which manifested as his previous incarnations' personalities arguing in his mind. Each incarnation went by a sequential number.
Biography
The One
In his first incarnation, the One worked in the Panopticon Archive, where he found information about a prototype of a stellar manipulator. He had a seat on the High Council. He left Gallifrey and became a criminal. (AUDIO: The Eleven, The Satanic Mill)
The Eight
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The Eight was an aberration compared to his other incarnations, attempting to be a "good man." Using meditation he was able to suppress the voices of his previous incarnations. He became involved with the Time Lords' (and his) future, attempting to stop the Eighth Doctor from assembling the Doomsday Chronometer. After he was killed by The Clocksmith, the Eight retreated into the Doctor's TARDIS and regenerated. (AUDIO: The Eighth Piece, The Doomsday Chronometer)
The Nine
After regenerating, the Nine claimed to be a new incarnation of the Doctor to Helen Sinclair and Liv Chenka. Rather than trying to be a "good man" like his predecessor, the Nine was motivated by kleptomaniac greed. Helen and Liv helped him to rob the archive on Gallifrey, but he abandoned Liv when she became suspicious. He took Helen hostage, and brought her to the Crucible of Souls. He attempted to use the crucible to gain immortality, and to exorcise his previous incarnations. After being thwarted by the Doctor, the Nine stole the Clocksmith's TARDIS and ran away. (AUDIO: The Crucible of Souls)
The Eleven
The Eleven was captured by the Seventh Doctor and imprisoned on Gallifrey.
When he escaped, he managed to steal a TARDIS. The Eighth Doctor was brought in to find him. He installed himself as President by an ancient edict as he created a state of emergency and the President was off-world. He used the Sash of Rassilon to freeze the Time Lords. (AUDIO: The Eleven)
The Eleven hired Fortuna and Cleaver to bring the Doctor to him. (AUDIO: The Galileo Trap)
The Eleven found the prototype stellar manipulator and planned to use the death of a Time Lord to activate it and destroy the Solar system. He captured the Doctor for these means. The Eleven's plans were prevented by an unknown force, and the Doctor's screwdriver signalled for the TARDIS to land near the Doctor, allowing him to escape. (AUDIO: The Satanic Mill)
He was once interviewed by Caleera for the archives, as he knew she was special. He convinced her to amplify her powers for his plans. (AUDIO: Scenes From Her Life) He then came to Syra as part of his plans with Caleera. He planned a trap in the mines to kill The Doctor. He tried to kill Liv in the mines until River Song stopped him. He wanted to use Caleera to destroy planets. (AUDIO: The Sonomancer)