End of the universe

The end of the universe, known to the Time Lords as "Event Two" and to others as the "Big Crunch", was an event that took place far off into the future in which the universe, or N-Space, collapsed in on itself due to being a closed system and entropy constantly building up.

Spatially, the end of the universe was also the "edge of the universe", where space actually ended and there was nothing except the Black Void where the Eminence existed. The Eighth Doctor also spoke of each individual having their own, personal end of the universe, referring to death. (AUDIO: Time's Horizon)

Projected dates
Before 1981, the universe had already passed the point of collapse. Having discovered this, the Logopolitans created Charged Vacuum Emboitments which opened N-Space into another universe, E-Space, allowing entropy into E-Space. Though Logopolis was destroyed in 1981, the CVEs were rebooted and continued to feed entropy from N-Space into E-Space. (TV: Logopolis)

The end of the universe was projected to occur in varied times, including the years 60,000,000,000 AD (AUDIO: Zagreus), 100,000,000,000,000 AD (TV: Utopia) and, in an alternate universe, 100,000,000,000,000,000,000,000,000,000,000 (One hundred nonillion, 1032) AD. (PROSE: The Infinity Doctors)

The Mandelbrot Set informed the Grey Man and Bernice Summerfield that, due to the actions of Gabriel and Tanith in 1994, the universe would now end "several metacenturies" earlier than projected. (PROSE: Falls the Shadow)

Attempts to end the universe
Dimensional transference was a theoretical phenomenon caused by a black light explosion that would potentially exhaust all energy in the universe. Intrigued by the uniqueness of this, Drathro allowed his black light converter to fail before he was stopped by the Sixth Doctor. (TV: The Mysterious Planet)

Donna Noble prevented the Daleks from destroying the universe, indeed every universe, using their reality bomb (TV: Journey's End) The Tenth Doctor later stopped the Time Lords from transcending into creatures of pure consciousness, which would have ended the universe and all other life. (TV: The End of Time)

Actual ends
The Kovarian Chapter of the Silence (TV: The Time of the Doctor) caused the universe to undergo total event collapse when they destroyed the Doctor's TARDIS, causing every star to explode at every moment in history. The Eleventh Doctor was able to "reboot" the universe using a restoration field. (TV: The Big Bang)

Species at the end
The Panjistri created the God Machine in an attempt to prevent the end of the universe. (PROSE: Timewyrm: Apocalypse)

The inhabitants of Ember attempted to survive the end by using the Somnus Foundation on 21st century Earth to transform humanity into a gestalt entity. They were defeated by the Fifth Doctor and Turlough. (AUDIO: Singularity)

The Toclafane, with the aid of, attempted to survive as well by travelling to 21st century Earth and murdering their ancestors. They were defeated by the Tenth Doctor and Martha Jones. (TV: Last of the Time Lords)

The Time Lords exist at "the end of the universe, give or take a star system or two", having moved Gallifrey there for protection when they emerged from the pocket universe the Doctor had placed it in. Due to the immortality that came with the medical kit applied to her, Ashildr was also found by the Twelfth Doctor, waiting in The Cloister in the bowels of The Capitol for the end of the universe. In her own words, she had been watching the stars die to pass the time until the end. However, she eventually left with Clara Oswald to drop the Doctor off in Nevada, and then to take Clara back to Gallifrey "the long way 'round." (TV: Hell Bent)

Visiting the end
Numerous advanced civilisations used the end of the universe as a dumping ground for dangerous items. The Third Doctor took Sergeant Kandula's body and the Tipping Device to the end of the universe and left them there. (PROSE: Midnight in the Café of the Black Madonna)

The Fourth Doctor and Romana II watched the universe end from some unknown vantage point. As the dimensions collapsed, the Doctor gave Romana the last Rolo in the universe. (PROSE: Do You Love Anyone Enough?)

River Song said that she and the Doctor had been to "end of the universe" together. (TV: Forest of the Dead)

During the Last Great Time War, to prevent the Time Lords from deploying the Tear of Isha into the Tantalus Eye, which would wipe out twelve planets in the Tantalus Spiral, the War Doctor hijacked Commander Partheus' TARDIS and travelled to the end of the universe. Cinder deployed the Tear into one of the last stars in existence, a red giant, and it collapsed, causing no harm to anyone. (PROSE: Engines of War)

Orson Pink was sent to the end of the universe after taking part in a 22nd century time travel experiment that sent him too far. The Twelfth Doctor found him trapped on the last planet in existence. (TV: Listen)

When the Doctor emerged from his confession dial on Gallifrey, he was at "the end of the universe, give or take a star system or two", Gallifrey having been moved there for its own protection. (TV: Hell Bent)

Other information
The Black Guardian was most powerful at the end of the universe, where his counterpart, the White Guardian, could not interfere. (PROSE: The Well-Mannered War)