- You may be looking for the member of Faction Paradox.
Since agents of the Service's past lives were erased, the details of Sabbath's pre-indoctrination identity was unknown. (PROSE: The Adventuress of Henrietta Street) He remembered glimpsing the Eleven-Day Empire as it passed from the British Empire to Faction Paradox in 1752. (COMIC: Bêtes Noires & Dark Horses)
Working for the Service
Sabbath was indoctrinated into the Service in 1762 at the age of 21. (PROSE: The Adventuress of Henrietta Street, AUDIO: Sabbath Dei) He specialised in engineering of the occult geometry of the Masonic movements. He was inducted on a Saturday (which may have inspired his Confirmation Name, by the Jewish cabbalistic trend in the Service) by being bound with thirteen chains, thirteen locks, and thirteen garters; covered with a hood of black sackcloth; hung with three hundred pounds of lead; and dropped into the Thames. He was certain of his death, and he believed he saw a vast Leviathan passing over him as a shadow while he lay on the bottom of the river, though that may have been the darkness of unconsciousness. He never emerged from the river, and he was presumed dead. (PROSE: The Adventuress of Henrietta Street) However, he was saved from this certain death to be used as a tool for off-planet powers: (PROSE: Sometime Never) he appeared dry and unharmed at Cambridge the following morning. (PROSE: The Adventuress of Henrietta Street)
Later that year, Sabbath attended the Hellfire Club's ball at Medenham Abbey, where he challenged Cousin Eliza to a game of pontoon where the loser of each hand would have to give a truthful answer to the winner's question. He forfeited the match when asked who his employer was, and he advised Eliza to look into the death of Mary Culver. He then followed the Sieur d’Eon into the cavern beneath the Abbey, where he met Cousin Justine and warned her the Service wouldn't let the Order of St Francis form an alliance with the Eleven-Day Empire.
Later, the Earl of Bute instructed Sabbath to investigate the Supplication of the Anakim ritual, which was reportedly performed by Mary Culver prior to her death; Sabbath performed the supplication ritual on himself and, rather than becoming fully possessed, simply became driven to serve the Great Houses by bringing Justine to justice. (AUDIO: Sabbath Dei) He found Justine at St James' Square and transformed the architecture into a courtroom in the jurisdiction of the Houses. When Justine challenged the validity of the Grandfather's crimes in the light of Lolita's violations of the protocols of history, Sabbath summoned Lolita to the courtroom to hear her testimony; after this testimony, met with no objection from the Great Houses' representatives, he dismissed Lolita and condemned Justine to the Homeworld's prison planet.
During this, he became an uneasy ally of Compassion-as-Culver in her plot against Lolita. Shortly after his ritual, he told Compassion (through Lord Sandwich) that he would keep out of her way if she kept out of his, and while taking Justine to trial he told Eliza and d'Eon where to find the automata. By summoning Lolita to the courtroom, he also gave them an invaluable chance to attack the automata. After the trial, his commitment to the Great Houses fulfilled, he visited Compassion to congratulate her on her victory over Lolita, telling her and her allies where to find Justine. (AUDIO: In the Year of the Cat)
After the War ended, Sabbath continued to work for the Service, eventually becoming its commander by 1774. He caught Cleeve and the American ambassadors to King George III performing an Anasazi ritual to the god Teskatsipotcha, and he sent the Service's Ratcatchers to catch Mayakatula. (COMIC: Bêtes Noires & Dark Horses)
In 1780, Sabbath defected from the Service and set up his own independent power base. He sent a message via a number of corpses of the Service's Ratcatchers saying, "leave me alone, and I'll leave you alone". (PROSE: The Adventuress of Henrietta Street) Shortly after this, at St. Cedd's College, Sabbath was approached by the Council of Eight, who warned him of the impending arrival of the Doctor. (PROSE: Sometime Never...)
Sabbath encountered "Leviathan" under the River Thames as part of his indoctrination ceremony into the Service. He set up his own power base independent of the Service. After leaving the Service, Sabbath sent a message via a number of corpses of the Service's "ratcatchers" saying, "leave me alone, and I'll leave you alone".
The Doctor chose Sabbath for his best man at his wedding to Scarlette. Sabbath later removed the Doctor's second heart, allegedly to cure the Doctor of an illness caused by the heart's attempt to connect the Doctor to the non-existent Gallifrey, but also allowing Sabbath to travel through time in the Jonah, endowing him with the Doctor's ability to penetrate "deep time" — exploring the universe beyond his home era and planet — that would have been impossible in his more primitive ship otherwise. (PROSE: The Adventuress of Henrietta Street)
Travelling through space and time
Sabbath had agents which were to him the same as companions were to the Doctor. Among them were Juliette Vierge, (PROSE:The Adventuress of Henrietta Street) Sasha and Jueves, (PROSE: History 101) Jaxa and Roja, former Time Agents, (PROSE: Trading Futures) and The Angel Maker (aka Elizabeth Kelly). (PROSE: Camera Obscura)
Sabbath arranged for the Doctor and the Clock People to meet on a Plutocratic Empire colony planet, manipulating the Doctor's perception of the situation so that he would see the creatures as a threat rather than evacuees. (PROSE: Anachrophobia) He later tricked the Doctor into destroying the System, a mysterious information-gathering program that allegedly contained information about his initiation that should not be made public. (PROSE: History 101)
While near death, Sabbath met Death, learning that the Doctor's second heart created a link between the Doctor and Sabbath that prevented the Doctor from dying; even if his chest was virtually crushed, one of his hearts was still beating in Sabbath. After this link resulted in the Angel-Maker sacrificing herself to save the Doctor in the belief that she would also save Sabbath, Sabbath tore out the heart, allowing the Doctor to grow a new one. (PROSE: Camera Obscura)
Sabbath was sent by his masters to take actions that would allegedly "collapse" reality into a single manageable timeline, convinced that time-travellers weakened reality by creating new universes every time they went back in time. This plan failed, and instead Sabbath's actions caused every parallel universe to overlap and fight for dominance. (PROSE: Time Zero) Realising that his plans had not worked, Sabbath kidnapped two of the Warlocks of Demigest and planned to use their powers to his advantage. He took the Warlocks in the Jonah to Selonart, where he attempted to become one with the universe due to the unique conditions on the planet. He planned to use the Warlocks to then help him control the universe. Sabbath's plan backfired due to the intervention of the Doctor and Bloom. Sabbath was then taken by the Warlocks back to Demigest where he was kept as their prisoner. The Doctor arrived later and killed the Warlocks, allowing Sabbath to escape. (PROSE: The Infinity Race) Sabbath later assisted Fitz Kreiner, Anji Kapoor and the Doctor when the multiple realities began to converge and mix. (PROSE: The Last Resort)
Sabbath was finally killed after turning his back on his employers and helping the Doctor; realising that his employers gained power from predicting future events, and with their plans now dependent on Sabbath killing either the Doctor or the head of the Council, Sabbath instead shot himself, something that the Council "knew" he wouldn't do. (PROSE: Sometime Never...)
In an alternate timeline, a version of Sabbath imprisoned Alan Turing, preventing the creation of the computer. He believed that his actions were to turn Turing into a temporal nexus whose death would cut Sabbath's world off from the rest of the multiverse and protect it from the catastrophe that had been unintentionally set off by the "prime" Sabbath, but in reality killing Turing just accelerated the multiversal damage. (PROSE: The Domino Effect)
Sabbath was generally opposed to chaos and believed that unauthorised time travel created parallel universes which threatened reality. Sabbath was confident in his mental abilities. Aided by the Doctor's second heart, he survived a journey into Death's realms. (PROSE: Camera Obscura)
He was incredibly stubborn and disliked beings who lorded their powers over others, including the Doctor. However, this arrogance also meant that he found it hard to admit when he was wrong, constantly convinced that he understood time better than the Doctor even after the Doctor provided evidence that time travel did not work the way Sabbath believed it did. (PROSE: Time Zero)
Sabbath used many pseudonyms, often variations upon his chosen name of Sabbath, such as Holiday or Mistletoe. (PROSE: Anachrophobia, Time Zero) Although he openly scorned his agents, he was fiercely loyal to them. (PROSE: The Adventuress of Henrietta Street)
Sabbath was bulky and muscular. His body was getting fat, having concluded that he was better served as a behind-the-scenes manipulator rather than taking action himself. He kept his head almost shaved. This was not a political statement or an attempt to intimidate people, but to save time and energy in grooming. (PROSE: The Adventuress of Henrietta Street) Many of Sabbath's clothing choices echoed the Doctor's; for example, he wore a linen suit after adopting the role of Time's Champion. (PROSE: Camera Obscura) Cousin Eliza said he looked nothing like Godfather Sabbath. (AUDIO: Sabbath Dei)
Behind the scenes
Agent of the Service - i.e. British intelligence - in 1762. To imagine Sabbath, imagine an eighteenth century Bond-figure who's been trained in ritualism in a time when there's a distinct occult streak running through the entire British establishment and the Service is largely run by Freemasons or Jacobites. Now imagine that he's a lot less smug and a lot less interested in copping off with people than Sean Connery would be, an agent who's dedicated to his job but still has a very definite kind of charm and a fierce (but understated) intelligence. At this point he's still a young operative, in his early-to-mid-twenties, but he's got an obvious talent for what he does and a genuine curiosity about the bizarre events now taking place. The idea is that although Sabbath's the opposition in this story, he's not actually the villain. If we don't find ourselves liking him then something's wrong.