Asylum Incident

The Asylum Incident was the Time Lord designation for the event in which Parliament of the Daleks tasked the Eleventh Doctor with destroying the Dalek Asylum. The Dalek Combat Training Manual composed by the Time Lords, which dated other events down to the century, could not identify the temporal co-ordinates of this incident. (TV: Asylum of the Daleks, PROSE: Dalek Combat Training Manual)

Background
The Dalek Asylum was a snowy and mountainous planet used by the Daleks as a prison and "dumping ground" for those among them who had malfunctioned, gone insane and/or become mentally scarred by battles. The Dalek Asylum was protected by a force field and a nanocloud, which converted beings that did manage to enter into Dalek puppets. The sane Daleks left their insane fellows in the Asylum rather than kill them because they epitomised the Dalek concept of beauty: pure hatred. Even the Daleks don't know how many of their brethren are incarcerated on the planet, but tell the Doctor through Darla that it's in the millions at least.

Even amongst the deranged Daleks, there was still an area described as "intensive care", which housed several Daleks who had survived conflicts with the Doctor on planets such as Spiridon, Kembel, Aridius, Vulcan, and Exxilon. (TV: Asylum of the Daleks)

According to human historians, a notable inmate of the Dalek Asylum was Rusty, a bronze Dalek who, in the Good Dalek Incident, developed a hatred of the Daleks which led him to defect to the Combined Galactic Resistance, which opposed their advance, before being captured by the Daleks. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) However, the Time Lords stated that Rusty's betrayal came after the Asylum Incident and the Siege of Trenzalore. In a moment that the Time Lords stated to be after the Hybrid Incident, (PROSE: Dalek Combat Training Manual) the Twelfth Doctor indeed visited Rusty billions of years in the far future on Villengard, aware that he had been fighting the Daleks all that time. (TV: Twice Upon a Time)

By the time of the Asylum's destruction, the residents came in multiple casings from across Dalek history. Among them were numerous bronze Daleks, a contemporary Black Dalek, a silver Dalek War Machine, an Elite Guard Dalek as seen at the start of the Dalek Civil War, a silver Dalek as seen on Exxilon, Grey Daleks including one as seen on Spiridon, two identical to the first Mark III Travel Machines unveiled by Davros, two as seen following the Dalek-Movellan War, two Renegade Daleks, an Imperial Special Weapons Dalek, a white Supreme Dalek and a Strategist Dalek of the New Dalek Paradigm. (TV: Asylum of the Daleks) The Supreme Dalek appeared without its eyepiece and with a damaged casing identical to that of a Supreme Dalek whose eyepiece had been removed by the Eleventh Doctor in an encounter which the Time Lords indicated as preceding the Asylum Incident. (TV: The Wedding of River Song, PROSE: Dalek Combat Training Manual)

The Incident
The Alaska had inadvertently breached the Dalek Asylum's force field and crashed into the planet. Junior Entertainment Manager Oswin Oswald was fully converted into a Dalek by the inmates, while the rest of the crew were converted into Dalek puppets by the Asylum's nanocloud. The Asylum was originally fully automated, but over the course of a year, Oswin was able to reduce the Asylum to a ruin by hacking into its systems.

A year after the Alaska crashed on the Asylum planet, the Parliament of the Daleks feared the insane Dalek inmates could escape. In order to destroy the planet and the Daleks inhabiting it, they kidnapped the Eleventh Doctor, Amy Pond, and Rory Williams, and sent them to the surface (by way of a gravity beam) in order to deactivate the planet's defences, as no Dalek was willing to infiltrate the Asylum themselves due to fear of the insane Daleks.

On the planet, the Doctor, Amy and Rory were guided by Oswin who was unaware of her status as a Dalek. Due to her hacking, Oswin could lower the Asylum's force field, but refused to do so until the Doctor rescued her from the escape pod she believed she was trapped in. The Doctor eventually reached the intensive care unit where the Daleks, who were normally completely catatonic, woke up in his presence due to their hatred of him. Before the Daleks could kill him, Oswin hacked the Dalek Pathweb and erased all memory of the Doctor from the Daleks to his shock as even he couldn't hack the Pathweb. Moments later, he learned of Oswin's conversion after finally finding her and she nearly gave into her programing in her despair over the situation. Breaking down, Oswin regained control and decided to end her own existence and that of the Daleks. Oswin lowered the Asylum's force field and ordered the Doctor to run and remember her.

As the Dalek fleet fired on the defenceless Asylum, the Doctor was able to use a teleporter to teleport himself, Amy and Rory aboard the TARDIS on the Dalek ship in orbit. Once the Asylum defences were down, the Daleks fired missiles at the planet, blowing it up and killing the Daleks trapped there, (TV: Asylum of the Daleks) though Rusty would later resurface on Villengard. (TV: Twice Upon a Time) To the Doctor's surprise, when he emerged from the TARDIS to taunt the Daleks after they detected his teleport, Oswin erased the knowledge of his existence from the totality of the Pathweb, not just among those in the Asylum. (TV: Asylum of the Daleks)

When the Great Intelligence invaded the Doctor's time stream on Trenzalore to turn all of his victories into defeats, the Dalek Asylum was one of the many places where the Doctor died. When Clara Oswald followed him into the time stream, it was revealed that Oswin Oswald was one of many versions of Clara scattered across the Doctor's history with the purpose of saving his life. (TV: The Name of the Doctor)

Aftermath
The sudden deletion of all information concerning the Doctor from the Pathweb caused the Prime Minister of the Daleks to spend whole centuries scrutinising over the mystery of the Daleks' forgotten enemy, going insane in the process.

300 years into the Siege of Trenzalore, the Daleks regained their memories of the Doctor from the cadaver of Tasha Lem. Upon regaining these memories, the Prime Minister dashed itself against its glass case; the Supreme Dalek declared it unfit for service and exterminated the Prime Minister, becoming the new leader of the Parliament of the Daleks before it was destroyed centuries later at the end of the siege, all but wiping out the Daleks from the perspective of observers barring their awareness of Skaro's survival. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)