The Dalek Time Squad was an elite battalion of Time-Sensitive Daleks deployed by the Emperor of the Restoration to attempt to exploit the "fluctuations in history" caused by the Tenth Doctor travelling back to the Dark Times and declaring war on the Kotturuh. (PROSE: The Guide to the Dark Times)
The Time Squad contained four individual members: the Dalek Time Commander, the ancient Dalek Prime Strategist, a Scientist Dalek and a Dalek Executioner. Time-sensitive silver Dalek drones of the "basic model" were assigned to the Squad and were not supposed to think for themselves, although River Song suspected otherwise. (PROSE: The Guide to the Dark Times)
The Dalek Emperor learnt that history was under attack and that the Doctor was involved after receiving a message from an ancient Dalek drone, who he deduced was the last survivor of a Time Squad that had yet to be sent back in time. (PROSE: The Last Message) Eventually, the Emperor formed the Time Squad to travel back in time to rectify the temporal fluctuations and return them to the Daleks' advantage. (PROSE: The Guide to the Dark Times) He also recorded a message for the event of the Squad failing to correct the timeline, outlining a contingency plan known as the "Ultimate End". (PROSE: All Flesh is Grass)
Recruiting the Doctor
The Time Squad captured the Eighth Doctor's TARDIS on Atharna, (AUDIO: He Kills Me, He Kills Me Not) planning to use it in order to travel back to the Dark Times where they could exploit the time fluctuations being caused there. (PROSE: The Restoration Empire) Oblivious to their true plans, the Doctor was asked by the Daleks for help, despite the Executioner's desire to exterminate him. They went to Wrax, nominally to analyse the changes to the planet's timeline, but the Daleks actually hoped to obtain the Wraxians' Devolver. After they made peaceful contact, the Doctor went with the Strategist to explore the Wraxian galleries whilst the Commander, Scientist and Executioner met the Wraxian President. She agreed to demonstrate the Devolver and consider an alliance with the Daleks, but betrayed them, planning to use the Devolver on the Daleks. The Commander ordered the Drones aboard the timeship to invade Wrax to stop her, whilst the Doctor and Strategist managed to reach them. Per the Strategist's urging, the Daleks let the Doctor negotiate with the President and he convinced her to dismantle the Devolver in return for the Daleks' withdrawal. He revealed he had a theory on the source of the fluctuations, but would only tell the Daleks when they had left Wrax. The Commander agreed, but secretly sent the Executioner back to Wrax to use the Devolver to wipe out the Wraxians. The Doctor told the Time Squad the alterations in time began in the Dark Times and connected his TARDIS to their timeship so they could travel back there. Whilst he did so, the Strategist conferred with the Commander, expressing his belief that the Doctor had been successfully manipulated. (AUDIO: The Enemy of My Enemy)
In the Dark Times
Tracing the alterations to Mordeela, (PROSE: All Flesh is Grass) the Eighth Doctor and the Daleks confronted the Tenth Doctor's Victis Fleet over the planet, alongside the Ninth Doctor in a Vampire coffin ship. (PROSE: The Knight, The Fool and The Dead) In the ensuing Battle of Mordeela, the Daleks tore apart the Victis Fleet, despite the Eighth Doctor's efforts to rein them in, but were forced back by Brian the Ood deploying a variety of ancient weapons. This enabled the Tenth Doctor's flagship, the last of the fleet remaining, to destroy Mordeela and flee. (PROSE: All Flesh is Grass)
The Daleks began a back-up plan of experimenting on life forms unique to the Dark Times to weaponise them. (PROSE: Mission to the Known) The Commander also ordered Dalek scout ships to wipe out the surviving Kotturuh, fearing they may judge the Daleks. The Eighth Doctor found himself sidelined, as the Daleks only needed him to ensure they could eventually escape the Dark Times. (PROSE: All Flesh is Grass) The Daleks invaded the planet, Velosia, assuming the façade of helping the Velosians fight off the Kotturuh, only to harvest the best and brightest Velosians and leave the surviving few on Velosia to await the Kotturuh. Afterwards, the Squad discovered an abandoned spaceship, where they and the Doctor found a source of Huon energy and the Daleks attempted to absorb it. They ran into difficulties until the Doctor helped them, prompting them to thank him for being their saviour again, to his discomfort. (COMIC: Tales of the Dark Times)
The Daleks began seeking a Great Vampire for their experiments. They attacked the Ninth Doctor's coffin ship, but the Eighth Doctor forewarned the Vampires so they could escape and met his future self to escape in his TARDIS. (PROSE: All Flesh is Grass) After the Doctor escaped, the Commander and Executioner received the pre-recorded instructions from the Emperor in the event of their failure to prevent the changing of history. The Emperor ordered them to take advantage of being in the Dark Times by destroying Gallifrey before the Time Lords existed. (PROSE: Mission to the Known) The Strategist was not privy to the orders, which the Commander and Executioner referred to as the "Ultimate End". The Strategist and Scientist continued their experiments, seeking to create a more biologically efficient form of Dalek known as the Dalek Symbiont.
The Daleks traced a fleeing Vampire, Ikalla, to Entranxis, where she had been captured by the Death Brokers. A scout ship invaded the planet, but Ikalla escaped due to the presence of the Eighth, Ninth and Tenth Doctors. As a Kotturuh ship approached the planet, the Daleks destroyed it and then used missiles to set Entranxis' atmosphere alight.
The Time Squad still managed to capture a Great Vampire. The Tenth and Eighth Doctors and Brian discovered this after finding a coffin ship the Daleks had raided and infiltrated the Dalek saucer using a surviving Bloodsman named Gelsin. The Tenth Doctor and Gelsin observed the final creation of the Symbiont by the Strategist and Scientist who infused a Dalek with Vampire DNA; as such the resulting creature could not be killed due to the fact it was already "undead". The Eighth Doctor and Brian went to the bridge, with the Doctor claiming his alliance with the Daleks still stood. They teased information about the Ultimate End and the Daleks killing the Kotturuh off from the Time Commander. The Symbiont experiment caused a power drain, allowing the Doctors and Gelsin to escape whilst Brian stayed behind. The Commander reprimanded the Strategist, claiming he had endangered the Ultimate End. The Strategist countered that he could not endanger plans he had been unaware of and presented the Symbiont. Brian infiltrated the engine room, connecting an explosive to the engines which he wired to himself to prevent the Daleks killing him. He informed the Doctors that the saucer's destination was Gallifrey and was rescued by the Tenth Doctor before the Daleks could kill him.
Realising the Doctors would now attempt to defend Gallifrey, the Strategist ordered for the Drones to be given the Symbiont DNA, creating an army of undying hybrid Daleks. This newly created army was used to invade Gallifrey whilst the original Symbiont was sent to kill the last Kotturuh, Inyit, on Birinji. The three Doctors made a final stand against the Daleks over Gallifrey, assisted by Coffin Ships of the Free Undead, and eventually decided to crash their ship into the Dalek saucer in the hopes that the resulting paradox would destroy them. Before their final move was necessary, however, the new army was defeated by Inyit, who used the last of her powers to pass judgement on the entire hybrid Dalek race. As the Daleks panicked, fearing the judgement might spread to pure Dalek DNA, the Eighth Doctor boarded the Dalek saucer and used a remote detonator to trigger Brian's explosive in their engines, forcing the saucer into the Time Vortex and out of the the Dark Times. (PROSE: All Flesh is Grass)
The Doctor continued to sabotage the Dalek saucer in the Time Vortex, leading to division between the Commander and Strategist over how to rectify the situation. The Commander favoured the Executioner and let it have autonomy to purge the ship of aliens, whilst the Strategist worked with the Scientist to stabilise the ship. The Commander also had the Doctor's TARDIS brought to the bridge to force the Doctor to confront him. The Doctor outwitted the Scientist by sabotaging the gravity in its laboratory and tricked them into cutting power from its lab. The Executioner became increasingly insane, damaging the ship further in its rampage to kill the Doctor and two aliens who had been released from cryogenic suspension. The Commander was unable to rein it in due to the autonomy he had granted it, to the Strategist's frustration. The Doctor caused the hull of the ship to break after detonating an explosive he had attached to the Scientist, leading to the saucer starting to break apart, and the Strategist attempted to bargain with him to escape in his TARDIS. The Doctor played along, but exposed the deal to the Commander on the bridge, leading to a firefight between him and the Strategist. The Commander was killed, prompting the Drones to turn on the Strategist as a traitor whilst the Doctor escaped. (AUDIO: Mutually Assured Destruction)
The Strategist survived the break-up of the saucer, observing the other Daleks being torn apart by the time winds. He used the Kotturuh crystals that he had stored in his casing to power an emergency temporal shift to escape the Time Vortex. (PROSE: Exit Strategy)
A single Drone survived the destruction of the Time Squad, ending up adrift in space. It sent a message warning about the Doctor and that history was under attack, which was picked up by the Emperor at the start of the crisis. (PROSE: The Last Message) The survivor eventually ended up in the Oort cloud. In 2985, it was brought aboard the Starship Future and reconstructed its casing. It attempted to a cultivate a new Dalek army from the dormant colonists, but was foiled by the Fourth Doctor. The Doctor believed it defeated, but it had actually survived. (AUDIO: Genetics of the Daleks)
The existence of the Time Squad was recorded in the Matrix. Though the Time Lords recorded the Squad as ruthless even by Dalek standards, they explicitly annotated that they had difficulty placing the Squad, and indeed the Restoration Empire as a whole, in what they knew as established Dalek history. (PROSE: Dalek Combat Training Manual)