Andromeda (galaxy)

The Andromeda Galaxy, also known as M31, was a galaxy located near the Milky Way, about 2.6 million light years from Earth.

History
A long time prior to 3999, the Wirrn attacked many worlds in the Andromeda Galaxy, including the Phylox system, Coscos, Salostopus, Golos and Vysp. They departed for the nearest galaxy, but returned home after their invasion attempt there failed. (PROSE: Placebo Effect) Mavic Chen, Guardian of the Solar System, attended the Intergalactic Conference of Andromeda some time prior to 4000. Planktus of the Outer Galaxies also attended. (TV: The Daleks' Master Plan)

The Harmony and Redemption planned to visit the Andromeda Galaxy as the fifth galaxy in their seven galaxy cruise. (TV: The Husbands of River Song)

Humans reached the Andromeda Galaxy by the time of Space Station Nerva's conversion into a space ark. They soon came into conflict with the Wirrn, whose breeding colonies were destroyed by human colonists. After a thousand years of fighting, the Wirrn were driven from the Galaxy. They came to call Andromeda "the old lands". (TV: The Ark in Space)

A hundred million years after humans visited the Andromeda Galaxy, the First Doctor's TARDIS landed in a planetoid-sized ship and an armada of smaller ships, travelling slower than the speed of light headed for Mutter's Spiral in order to conquer it. The ship contained the One, made up of millions of Andromedan minds, life forms from the Andromeda Galaxy and Aalas, the android servants of the One. (PROSE: Doctor Who and the Invasion from Space)

At some point, there were high tensions between the organic and mechanical lifeforms in the Andromeda Galaxy, exemplified by the rise of the Cult of Shining Darkness. Andromeda was home to Humanoids as well as several nonhumanoid forms. The Tenth Doctor considered his knowledge of Andromeda to be spotty. (PROSE: Shining Darkness)

After feeding on the energy of the Bellatrix nova, the Sentience departed for Andromeda to feed on a supernova there. (PROSE: Nightshade)

Behind the scenes

 * According to background information given in FASA's The Doctor Who Role Playing Game, the android Movellans originated in Andromeda before being expelled from that galaxy by a coalition of races known as the Organic League.