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". (PROSE: The Game of Death)
The Face of Boe was said to be from the Silver Devastation. (TV: 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. (TV: Utopia)
The Tenth Doctor encountered an asteroid that shouldn't have been in the middle of the Silver Devastation. It contained blood-sucking monsters from another universe. (PROSE: The Game of Death)
Behind the scenes
Russell T Davies stated on the Utopia DVD box set commentary that Yana's memories were true. Davies said of this backstory: "He was a baby. A human baby. Because that's what the Master did — he was so frightened and terrified that he wiped himself as a baby and found on the Silver Devastation."