The Time Lords of Gallifrey designated the Seriphia Galaxy as Galaxy 17A53. The galaxy was part of the Local Group – a cluster of galaxies that were (in inter-galactic terms) in close proximity to each other.
The Seriphia Galaxy was unremarkable. A large, spiral galaxy with a normal rate of growth,it developed in the same manner as any other galaxy, with life evolving on a number of worlds, some intelligent and some not. Both aggressive and non-aggressive life forms evolved and developed technologies according to a vast number of philosophies and ecological challenges.
Seriphia was approximately four-hundred thousand (400,000) light-years in diameter, making it four times larger than Mutter's Spiral. Containing over six-hundred billion (600,000,000,000) stars. A wide diversity of planetary ecologies existed resulting in a vast amount of life-forms evolving in the galaxy.
This all changed after ten million years of development, when the Daleks unleashed the Apocalypse Element into the heart of the galaxy during their first attempted invasion of Gallifrey. This element had the potential to completely destroy the universe if left to its own ends and the Daleks and Time Lords were forced to work together to contain the effect. This they managed, but by this time, life throughout the entire Seriphia galaxy had been consumed.
Using their temporal technology, the Daleks accelerated time in the galaxy to speed up the development of new life. They then invaded the galaxy and enslaved it’s people before they developed sufficient technology to pose a threat. In this way, Seriphia became the base of operations for the Second Dalek Empire before they returned to their home galaxy to reclaim Skaro.
