Silver Devastation

The Silver Devastation was an area of space in the Isop Galaxy where two galaxies collided some hundred billion years ago. This vast sector of space contained nothing but dead Stars and dark matter. From a great distance it looked like a huge silver sea hanging in space, the edge area being commonly referred to as its ‘coast’.

History
The Face of Boe was said to be from the Silver Devastation. (DW: The End of the World)

Professor Yana was found on the edge of the Silver Devastation, a naked orphan in the storm with nothing except for a strange fob watch (Although it is possible that the Chameleon arch created these memories). (DW: Utopia)

The Doctor encountered an asteroid that shouldn't be in the middle of the Silver Devastation. (TDL: The Game of Death)

Myths and rumours
Many rumours surrounded the Silver Devastation such as:
 * It being populated by the mutant survivors of the two galaxies.
 * It being populated by refugees from the Old Time caught in eternal conflict.
 * Being only a void or bottomless chasm in time and space.
 * It containing blood-sucking monsters from another universe. (TDL: The Game of Death)