First Flux event

The First Flux event, also referred to as the Beginning of the End, (TV: Once, Upon Time) occurred on 31 October 2021, but it also rippled destruction and chaos throughout time in the Great Disruption. It was followed by the second and final Flux event on 5 December.

Prelude
The Flux was created to destroy the universe, (TV: Once, Upon Time) using anti-matter, (TV: The Vanquishers) by the Division who, under the leadership of Tecteun, had decided to abandon the universe for the next one, Universe Two. (TV: Survivors of the Flux) The Flux's impending arrival rallied the Sontarans, Weeping Angels, Ravagers, and "other species from across the universe". (TV: The Flux is Coming...) The Sontarans learnt of the imminent event, and the conflict it would provoke, from the assessment of Psychic Surveyor Kragar. They believed it would dwarf every previous conflict in history. (TV: The Halloween Apocalypse)

Having been apprehended by the Division during the Siege of Atropos, (TV: Once, Upon Time) was imprisoned in a containment chamber on the Burnished Rage battleground, allegedly at "the dawn of the universe". Every thousand years, agents of the Division would come check whether he was still secure in his containment; En Sentac visited him a number of times over the millennia, though they did not know if he had literally been there since "the dawn of the universe". During this time, he "planned" and "waited". (TV: The Halloween Apocalypse)

In what would become En Sentac's last such tour, performed in the company of K-Toscs, (TV: The Halloween Apocalypse) the "Awsok" Tecteun decided to "reintroduce" the Ravagers by releasing Swarm, (TV: Once, Upon Time, Survivors of the Flux) remotely disabling all the technology keeping him frozen. Shortly before this occurred, Swarm reactivated an old psychic connection he had with the Doctor, linking himself to the Thirteenth Doctor, (TV: The Halloween Apocalypse) as part of a long con to gain access to the Division's base outside Universe One. (TV: Survivors of the Flux) Using his powers to freeze En Sentac in place, Swarm kept his warden paralysed for a few moments before draining their life force. He renewed himself, screaming in exultation, becoming a taller,. (TV: The Halloween Apocalypse)

After completing his regeneration, the new Swarm relished at being renewed in a healthier, more slender form. Stepping out of the containment chamber, he reduced K-Toscs to ash with a single touch and recited a mocking "Trick or treat" to the Thirteenth Doctor, announcing that "[his] time had just begun". He travelled to Earth, to a remote house where Azure, his sister, was hiding in a human guise unaware of her true nature. He killed her partner Jón and then stripped the human guise from her, awakening her true self. (TV: The Halloween Apocalypse)

The Event
When this mysterious force appeared near Observation Outpost Rose, the entirety of the Thoribus Section was destroyed. While reporting the unfolding events, observation officer Inston-Vee Vinder had no choice but to evacuate the outpost. His station was destroyed moments later, consumed by the Flux as it advanced. (TV: The Halloween Apocalypse) The Flux ripped through Inston-Vee Vinder's home planet, devastating it. (TV: Once, Upon Time)

The Flux caused damage to the inner sanctum of the Temple of Atropos on the planet Time, leaving two Mouri broken. This caused time to begin to run wild, beginning the Great Disruption. (TV: War of the Sontarans)

A species recall was initiated, with 7 billion Lupari travelling to Earth aboard ships built to withstand the Flux to rescue humanity, who they were species bonded to. Karvanista, the Lupar bonded to Dan Lewis as his paired guardian, arrived early and abducted Dan from his home in Liverpool in order to protect him from this incoming threat. The Thirteenth Doctor was first told about the Flux by Karvanista himself, when she arrived to recover Dan, ostensibly to return him to Earth.

Attempting to observe the event up close, the Doctor witnessed the Flux reaching the edge of Earth's solar system, only for it to turn towards her TARDIS. As she fled the wave, the Doctor directed the Lupari, through Karvanista, to fly their fleet into a particular formation around Earth, together forming a protective barrier, which she hoped would keep the Flux from reaching it. With the Flux closing in on her TARDIS, the Doctor unleashed vortex energy from within the TARDIS control console. (TV: The Halloween Apocalypse) While the interactions of energies stopped the first Flux event from completely destroying the universe, (TV: Survivors of the Flux) it caused several system malfunctions in the TARDIS and caused the ship and its occupants to fall through time. (TV: War of the Sontarans)

Aftermath
The Flux had destroyed "many galaxies", leaving Earth at the epicentre of what remained. (TV: Survivors of the Flux)

Whilst "time ran wild", various factions began attempting to assert their power in the aftermath of the Flux. On her travels, Bel observed the Daleks, Cybermen and Sontarans taking control of sectors of the galaxy. (TV: Once, Upon Time) The Sontarans invaded Earth just before the Lupari shield came into effect, occupying Liverpool and preparing to embark on invasions throughout Earth's history, beginning in the Crimean War where they rewrote history. The Doctor repelled their incursion in the Crimea and Karvanista rammed a Imperial Sontaran Time Carrier into the rest of the fleet in Liverpool, causing a temporal implosion which erased the Sontaran invasion from Earth. (TV: War of the Sontarans)

The Doctor was able to repair the Temple of Atropos with the aid of the Mouri, returning time to normal. However, the Great Disruption had lasted long enough to release particles of the Time Force which would erode whatever they touched. (TV: Once, Upon Time)

Some survivors of the Flux gathered on the planet Puzano, as it was the only planet even partly intact in its quadrant. They were visited by Azure who tricked them into believing that she could take them to safety in another galaxy so that they would willingly enter her Passenger form. (TV: Village of the Angels) Swarm and Azure used these captives to strengthen the Time Force to create a psycho-temporal bridge to Division Control located outside the universe, where they killed Tecteun. (TV: Survivors of the Flux)

The Sontarans returned to occupy Earth weeks after their first attempt, now working with the Grand Serpent who had compromised Earth's defences from within. The Sontarans killed all of the Lupari in orbit, save Karvanista who escaped with the aid of the Doctor, and took their fleet for themselves. Swarm and Azure used the Division's technology to generate the planned second Flux event to wipe out the remaining universe, intending for the Temple of Atropos to be the last to fall, releasing Time. They planned to then rewind the destruction and play it out again repeatedly.

The Sontarans' psychic command, under the leadership of Kragar, used human psychics to predict where the Flux event would begin. Under the pretence of forming an alliance, they lured a Dalek and Cyberman fleet to the location, planning for their matter to resolve the Flux whilst their fleet sheltered behind the Lupari ships. The Doctor sabotaged their plan by helping Karvanista seize control of the Lupari fleet, whilst Vinder and Bel destroyed the command ship's communications to stop the Sontarans reacting in time. At the same time, at the request of the Doctor, the Division's Ood did his best to minimize the impact of the Flux so as to make it easier to stop. The Flux destroyed the gathered fleets of Daleks, Cybermen and Sontarans, however, this proved insufficient to stop it and some of the Flux was able to make it past the Lupari shield. Following a suggestion by Diane, the Doctor put Swarm and Azure's Passenger in its path and the matter within the endless prison proved enough to end the Flux with Time describing the Flux as being "extinguished". (TV: The Vanquishers)

One week later, Dan stated the Doctor had "saved" the universe through her actions. (TV: Eve of the Daleks)