The Nine Gallifreys or Nine Homeworlds project involved the crypto-forming of eight planets into cloneworlds of Gallifrey during the War in Heaven. (PROSE: The Shadows of Avalon, The Book of the War) However, the count of "nine" was implied to be an understated misnomer, as each secondary Homeworld created its own tertiary Homeworlds; some House Military strategists hoped this would end in every planet in the universe being turned into a Homeworld, (PROSE: The Book of the War) with hundreds of duplicates of Gallifrey being used as sheer ballistic projectiles by the end of the Last Great Time War as the scale of the War increased to unmanageable levels. (PROSE: Revenge of the Nestene)
The Nine Gallifreys project was originally planned by Greyjan the Sane (PROSE: The Ancestor Cell) and was spearheaded by House Mirraflex's Lady Armourer Mantissa and House Lineacrux four-hundred years later. (PROSE: The Book of the War)
Officially, each Homeworld was run by a caretaker House as a potential replacement if the original Homeworld were destroyed. However, many of the backup Homeworlds actually acted as decoys, with each having its own War King or War Queen and thinking it was the original.
There was a supposedly-total ban on contact between Homeworlds, but Mantissa eventually went into exile on one of the duplicates, (PROSE: The Book of the War) and by the time of the fall of Mictlan, travel between Gallifreys was often performed by the Lord President and his agents. However, even then, it was rumoured that not even the President knew which was the original. (PROSE: The Taking of Planet 5)
Some Gallifreys were hidden in pocket universes; (PROSE: The Taking of Planet 5) one Great House (AUDIO: The Eleven Day Empire) notably created a homeworld on Christine Summerfield's Earth in a bottle universe. (PROSE: Dead Romance) A human colony-world was cryptoformed by the Great Houses into a Homeworld between 3560 and 3591, and some of its inhabitants like Verrifant were mutated into regen-inf soldiers. (PROSE: The Book of the War)
Six years before the Cataclysm, the War King became President of what purported to be the original Homeworld, and he continued in that role for over half a century. (PROSE: The Book of the War) When Compassion became the first 102-form timeship two years before the War, (PROSE: The Book of the War) Romana was also War Queen and "Mistress of the Nine Gallifreys" on another Gallifrey. (PROSE: The Shadows of Avalon, The Ancestor Cell)
Sometime after the wiping of the original Gallifrey, Homunculette was taught the basics of escapology by War Cardinals at a training complex on Gallifrey XII. (PROSE: Alien Bodies) Homunculette and the the War King once visited Gallifrey Eight, which contained loomstacks and chronoforges to create weapons and soldiers for the Time Lords; D-Mat Guns were stored on Gallifrey Nine. (PROSE: The Taking of Planet 5)
Romana III's Gallifrey was invaded by Faction Paradox and destroyed sometime before the Eleven-Day Empire was destroyed (PROSE: The Ancestor Cell) in the War's fiftieth year; (AUDIO: The Shadow Play) at that time, the Faction claimed to have written that version of Gallifrey's backups out of existence. (PROSE: The Gallifrey Chronicles)
Several planets appeared to be the remnants of ruined Homeworlds: the legendary world Ardethe in the constellation Kaster Major was populated only by the Shabooj'm; (PROSE: Deadfall) the lifeless planet New Alexandria had the same coordinates as Gallifrey; (PROSE: The Crystal Bucephalus) and Winkle's Wonderland occupied the ruins of Rassilon's Foundry toward the end of the universe. (AUDIO: Zagreus)
Upon mishearing its name, Fitz Kreiner thought that Gallifraxion Four was a Gallifrey. (PROSE: The Tomorrow Windows) The planet was colonized by the Clock-People, (PROSE: Out of the Box) the remains of Mathara's Faction Paradox fleet (PROSE: The Story So Far...) following the Eighth Doctor's destruction of Romana III's Gallifrey. (PROSE: The Ancestor Cell)
Despite the destructions of so many Homeworlds, Entarodora argued in her lecture that the total number of War-time deaths by Great House members was nonetheless small because the inhabitants of these other Homeworlds were "mere-sheath echoes" of a "core probability". (PROSE: The Brakespeare Voyage)
In a dissenting account of the end of the Last Great Time War, claiming that the Eighth Doctor used the Moment to end the conflict, it was "Gallifrey Original" which convulsed and burst into flame as it was destroyed. (PROSE: Doctor Who and the Time War) In another account, it was his successor, the War Doctor, who destroyed the planet. (COMIC: Sky Jacks) However, most accounts claimed the War Doctor had almost used the Moment to destroy his Gallifrey, only to team up with his other selves to save the planet instead, with no hints of there being any other homeworlds active in the universe. (TV: The Day of the Doctor)
Behind the scenes
In 2022, Simon Bucher-Jones espoused the belief on Twitter that the version of Gallifrey shown in the Thirteenth Doctor television stories Spyfall, Ascension of the Cybermen and The Timeless Children as having been ravaged by the Spy Master was not Gallifrey Original, but one of seven surviving duplicate Gallifreys.