Tiberian Spiral

The Tiberian spiral galaxy was a galaxy that was destroyed in its entirety by a human empire in order to defeat a Cyberman army. It contained, according to Porridge, "a million star systems, a hundred million worlds" and "a billion trillion people." After its destruction, nothing of the galaxy was left, just a black, gaping hole in space easily identified by an outwards swarming bluish "ring" around the general area. The destruction of the galaxy effectively wiped out almost all Cybermen in the known Universe, to the point that most believed them to be extinct. Unbeknownst to the human empire a small number of Cybermen survived and began rebuilding their forces on the planet Hedgewick's World of Wonders. (TV: Nightmare in Silver)