The Matrix

The Matrix, officially called the Matrix of Time, (PROSE: Mindwarp, PROSE: The Quantum Archangel) was a supercomputer, a micro-universe used by the High Council of the Time Lords as a storehouse of knowledge to predict future events, maintained by the Keeper of the Matrix. As TARDISes possessed their own matrix, every Time Lord and TARDIS was connected to the central Matrix on Gallifrey where their experiences were constantly being uploaded. (COMIC: Sky Jacks)

Characteristics
The Matrix, specifically, contained a simulated reality environment, once described as a "micro-universe" (TV: The Ultimate Foe) which stored the personalities of Time Lords now without physical bodies and even the past incarnations of living Time Lords (COMIC: The Forgotten) within the APC Net, which cross-checked the data within the Matrix. (AUDIO: The Inquiry)

It functioned both as a "crypt" and a stone circuit board, and used Cloister Wraiths and "filed" Daleks, Cybermen and Weeping Angels attached to living "fibre optic cables" to guard the Cloisters as a "firewall". It could also ring the Cloister Bells in the event of impending catastrophe. (TV: Hell Bent)

Matrix data slices served as hard-drives that contained the virtual reality, (TV: Dark Water) which could also be projected around individuals, described by Coordinator Narvin as immersion in the five-dimensional episodic interface of a Panoptric network. The Eighth Doctor was impressed he didn't need to wear "silly plastic glasses." (AUDIO: The Death of Hope)

Romana II explained that when connected to the Matrix, the user was outside of real spacetime, "alone on the astral plane." (AUDIO: The Inquiry)

All Time Lords were connected to the Matrix on a basic level, (AUDIO: Pandora) and the Matrix stored the memories of dead Time Lords in a framework of electrochemical cells. (TV: The Deadly Assassin)

It was not only a record of the past, but could predict the future as well (TV: Arc of Infinity) by generating prophecies out of algorithms. (TV: Hell Bent)

The amount of knowledge in the Matrix, though vast, was not complete, and could be tampered with, given access. The unauthorised extraction of a Time Lord's bio-data from the Matrix was an offence tantamount to treason. (TV: Arc of Infinity)

A particularly skilled person such as the Valeyard could create images of events that never had happened nor ever would. (TV: Mindwarp, Terror of the Vervoids, The Ultimate Foe)

Whenever anyone used the Matrix to acquire a specific piece of information, a safeguard would cause anything else the user accidentally stumbled across to be wiped from their minds. (PROSE: Timewyrm: Genesys)

If two or more incarnations of the same Time Lord accessed the Matrix simultaneously, they all gained equal access to all other incarnations' memories. Because of this, a young, pre-Key to Time version of Romana I instantly understood her future when Lady President Romana II joined her in the Matrix. Additionally, sections of the Matrix could be partitioned, trapping entities in sections cut off from the rest of the Matrix. (AUDIO: Lies) Following the Last Great Time War, the length of the Matrix's database was eclipsed by the Dalek pathweb, leading the Twelfth Doctor to identify a unknown face through the latter. (TV: Twice Upon a Time)

Environment
To living beings, the Matrix could appear like conventional reality, (TV: The Deadly Assassin, The Ultimate Foe) a surreal dream, (COMIC: The Tides of Time) a dark void with lines of light(TV: Arc of Infinity) or first one, then another. Physical laws were malleable to the will of the inhabitant. Experience and sheer will gave one control over "reality". For example, the Fourth Doctor shouted, "I reject it," and his wounded leg instantly healed; this was undone by a more skilled Time Lord. (TV: The Deadly Assassin)

Beings known as the Matrix Lords, including Rassilon himself, "lived" there and could direct actions in the universe. They created a physical agent, Shayde, to act for them in the outside world. (COMIC: The Tides of Time)

Physical access
Living beings could access the Matrix through an apparatus connected to the head of the user. (TV: The Deadly Assassin) The Crown of Rassilon worn by any Time Lord gave them instant access. (TV: The Invasion of Time) The Keeper of the Matrix held the Key of Rassilon, granting access to the Seventh Door, thought legendary until the Doctor used the Key to access it. The Seventh Door allowed physical access to the Matrix. (TV: The Ultimate Foe)

Knowledge
Information was added to the Matrix, being imprinted on the nexus, as it was discovered by Time Lords, (AUDIO: The Wings of a Butterfly) being organised by the recorders living within the Matrix. (AUDIO: Neverland) Additionally, all events that occurred in the Capitol were recorded in the Matrix, (AUDIO: The Inquiry) and it also received data from sensors in TARDISes. (PROSE: The Quantum Archangel)

Many facts, figures, and formulas were contained within the Matrix, including faster-than-light travel, anti-gravity power, dimensional transference, (TV: The Mysterious Planet) how to build the De-mat Gun, (TV: The Invasion of Time) the threat posed by the Timewyrm, (PROSE: Timewyrm: Genesys), quantum mnemonics from the pre-universe, (PROSE: Millennial Rites) the Spinward Corporation and Arcadia in the 25th century, (PROSE: Deceit) America in the 1950s, (PROSE: First Frontier) history from the Humanian, Sensorian, Sumaran, and Rassilon Eras, (AUDIO: Neverland) and the Sanctuary on Bukol. (PROSE: The Golden Door)

Darker knowledge contained within the Matrix included the doomsday weapon on Uxarieus, (TV: Colony in Space) the Earth's sleeping races, (TV: The Sea Devils) the mechanics of the Source of Traken, (TV: The Keeper of Traken) the location of the Nestene homeworld, (TV: Terror of the Autons) the name of the last of the Dæmons, (TV: The Dǣmons) the deathworms, (TV: Doctor Who) the Crystal of Kronos and its relationship with the Chronovores, (TV: The Time Monster) the army of Daleks on Spiridon, (TV: Planet of the Daleks) the Martian GodEngine, (PROSE: GodEngine) the psychic parasites of Bellerophon, the frozen gods of Volvox, the political machinations of the Amentethys, the Proculus and their offspring the Scerbulus, the forgotten knowledge of the Kirbili, and limited information on the Constructors of Destiny concerning the Midnight Cathedral. (PROSE: The Quantum Archangel)

There was also a section of the Matrix known as the Slaughterhouse, compiled by the Celestial Intervention Agency, which contained a whole armoury of theoretical weapons, including the Profane Virus of Rassilon and, in a parallel universe, the Armageddon Sapphire. (PROSE: The Quantum Archangel)

Uses of the Matrix
Returned to Gallifrey by Councillor Goth, used the Matrix, secretly infiltrating it and using Goth as his agent within it. Goth confronted the Fourth Doctor there and attempted to kill him. (TV: The Deadly Assassin)

As Lord President, the Doctor used the Matrix to gain access to the secrets needed to defeat the Sontaran invasion of Gallifrey, specifically the De-mat Gun. (TV: The Invasion of Time) While connected to the Matrix, he learned of the existence of the Timewyrm (PROSE: Timewyrm: Genesys) and Quantum mnemonics. (PROSE: Millennial Rites)

After his supposed execution to stop Rassilon's exiled contemporary Omega from returning to the universe of matter, the Fifth Doctor hung suspended in the Matrix. Omega also had access to the Matrix. (TV: Arc of Infinity) One of the many versions of Clara Oswald created after she entered the Doctor's time stream appeared in the Matrix and saw the Fifth Doctor when he was sent there. (TV: The Name of the Doctor)

The Valeyard established a stronghold, the "Fantasy Factory", in the Matrix as part of his plan to steal the Sixth Doctor's remaining regenerations. During his attempt to stop him, the Doctor, as well as, entered into the "dreamscape" therein, the latter taking his TARDIS (or an illusory version of it) there. The Valeyard somehow took over the Keeper of the Matrix. (TV: The Ultimate Foe)

The Seventh Doctor confronted the Dark Matrix, which was trapped inside a TARDIS as it imploded. (PROSE: Matrix)

Fate of the Matrix
An ancient Gallifreyan evil named Pandora also survived and emerged from a special partition within the Matrix. Lady President Romana was eventually able to destroy the entity by seemingly destroying the Matrix itself. (AUDIO: Warfare) However, Romana later discovered that it had only been damaged. (AUDIO: Ascension)

After Gallifrey was destroyed by the Eighth Doctor in the War in Heaven, the Time Lords survived within the Matrix, which had been downloaded into the Doctor's mind - although he had to sacrifice much of his memory to make space for it. Their reconstruction was possible, but required a sufficiently advanced computer. (PROSE: The Gallifrey Chronicles)

In the final moment of the Last Great Time War, the deaths of every Time Lord being uploaded to the Matrix allowed it to gain sentience. The Matrix survived the end of the Time War by uploading a copy of itself into the Doctor's TARDIS. The Matrix then posed as the Hypothetical Gentleman, and tried to break out into the universe. (COMIC: Sky Jacks)

The Hypothetical Gentleman projected images of a quantum resonator into Emily Fairfax's mind, convincing her husband and herself that she was being contacted by an angel. After the pair built the machine, he linked it to the TARDIS to power it. He came out of it, to find a police officer, whom he sucked the time out of, leaving him frozen in time. The Eleventh Doctor called in Emily and Charles Fairfax to determine what the machine was about, and left to find the power source. The Hypothetical Gentleman then sucked out the time from Rory Williams. When the telepathic Emily read the Gentleman's mind, it was filled with images of Sontarans, a peg doll, a Zygon, a Kroton, a Headless Monk, a Silent, a Weeping Angel, and a Krynoid. He subsequently sucked the time out of Charles Fairfax, deeming the meal, "An insufficient morsel." He disappeared. The Doctor was examining the victims, when he returned, and the Doctor asked who he was, because he could write in High Gallifreyan. The Gentleman didn't provide an answer, and instead taunted the Doctor with the unknown knowledge. He then promptly began to steal the Doctor's time, which would have given him his own reality, but Amy Pond smashed the quantum resonator, apparently sucking him back into his hypothetical world. All of the victims were freed. As the Doctor, Amy, and Rory tried to leave in the TARDIS, the control panel sparked, surprising the Doctor, and he described it as the TARDIS having an upset tummy, and that it was nothing to worry about. It was shown, however, that the Hypothetical Gentleman was the cause, and that he was hiding on the TARDIS. (COMIC: Hypothetical Gentleman)

The Matrix attempted to fight the Doctor's TARDIS for control of its systems, and ultimately won, trapping the Doctor and Clara Oswald inside. The Matrix then created a wormhole to escape from the TARDIS into the wider universe. The Doctor stopped the Matrix by connecting both ends of the wormhole together, trapping the Matrix forever. (COMIC: Sky Jacks)

used a Matrix data slice to store the minds of the recently deceased into a data cloud so that the emotions could be altered and upgraded once their minds were downloaded back into converted Cybermen. (TV: Dark Water, Death in Heaven)

After Gallifrey returned to the universe, the Matrix was located below the Capitol in the Cloisters. (TV: Hell Bent)

Alternate timeline
In an alternative timeline the Matrix was invaded by the Cybermen. (COMIC: Prologue: The Sixth Doctor)

Matriz